170-01a-mar30.mp4: Meeting 1, March 30, 2021

0:00 syllabus - who should take this course and what you'll learn
5:30 about contract grading and how its used in this course
23:00 about the sound prompts (Ozzie and Harriet laugh and Wilhelm scream)
24:40 intro to Audacity sound editor, to play laugh track
29:11 Wilhelm scream sample
36:00 Pure Data and the acoustics library
37:00 spectrum of a sinusoid using Pd acoustics library
40:30 how to make patches using the Pd acoustics library
42:00 the path in Pd (how to get Pd to find the objects in the library)
43:00 the library as a directory
44:00 the file 1.LIST.pd - all the objects.  How to get help.
44:30 the "sinusoid" and "record" library objects.
45:00 edit mode and run mode in Pd
49:30 installing Pd on Microsoft windows
50:00 (three minutes of flailing)
54:00 downloading Pd on Windows
56:00 downloading the acoustics library
57:00 adding acoustics library to the Pd search path
58:00 oops, have to find where it went and unzip it
1:00:00 finally succeed in adding folder to path


170-01b-apr1.mp4: Meeting 2, April 1, 2021

0:00 incitement: dumb card trick
1;30 warning about in-ear headphones
3:30 first version of dumb card trick movie
4:30 how audio and image work together in a movie
5:00 version 2 of dumb card trick
6:00 version 3.
7:30 different functions of sound and image in a movie
10:00 more about the example and choices made in making it
14:00 why the smiley face?
17:30 more about video sound tracks
19:20 back to course organization and contract grading
24:00 make sure you have version 6 of Pd acoustics library
26:30 course "canvas" page
31:00 the Pd acoustics library: the "record" object again
32:30 setting length of the recording
34:00 listening to output of the "record" object
36:30 the "meter" object
37:00 using audacity to see the individual audio samples. Sample rate.
39:00 resolution (word size) of an audio recording
40:00 basic properties of a recording: sample rate, word length, number of channels
40:30 the PCM and compressed audio format (only use PCM for Pd or Audacity)
42:30 recording a sinusoid using the acoustics library
43:00 peak amplitude of a sinusoid.  Meaning of amplitude.
45:00 the meter shows average amplitude in two units (RMS and decibels)
45:30 frequency and starting phase (with amplitude, 3 properties of a sinusoid)
47:00 chapter 1 of the course notes: sinusoids
49:00 decibel scale
51:00 difference between acoustic amplitude and amplitude of a recording
52:00 two stages of conversion: sound/voltage and voltage/binary
54:00 what changing amplitude and frequency of a sinusoid sounds like
56:00 changing the amplitude and the frequency of a recorded waveform
57:30 the "multiply" object can change (scale) the amplitudes in a recording
1:01:00 mathematical description of changing frequency and amplitude
1:03:00 what "up" and "down" mean for amplitude and frequency
1:05:00 amplitude range of audio (-1 to 1 externally but freely variable in Pd)
1:06:00 average amplitudes shown by the "meter" object
1:07:00 multiplication by 0.1 decreases RMS by 0.1 and lowers decibels by 20
1:08:30 definition of RMS (root mean square) average
1:10:00 decibels are for describing proportions between amplitudes
1:12:00 more about decibels: multiple gain stages
1:13:30 what "gain" means
1:15:00 difference between dB (decibels) on meter and dB in "output" object
1:18:30 reminder: know your IA


170-02a-apr6.mp4: Meeting 3, April 6, 2021

0:00 incitement: phased looping inspired by Steve Reich's Piano Phase
3:00 reading sounds into "record" object: set length first
6:00 second copy in a second "record" object
7:00 playing the two loops together
9:00 relative phase of two sound loops
13:00 musical example: Charles Dodge, Any Resemblance Is Purely Coincidental
16:00 subject of the original opera aria ("Vesti la Giubba")
17:20 closer examination of the first 30 seconds of the piece
19:00 importance of the visual component of the piece
20:30 about the endlessly repeated word "recitar"
21:30 implications of using Caruso's voice in a 20th-century musical language
24:20 the dissected laugh
29:00 modern echos: "sampling"
31:30 ending: recognizable "money notes" and return (and fadeout) of orchestra
35:30 "great moments in opera" TV commercial
37:00 organization: back to the course canvas page; about projects and labs
51:00 More about using Pd: inputs and outputs and connections
52:00 why logarithms? demonstration of changing frequencies and amplitudes
59:30 sinusoid animation to see waveform, frequency and amplitude another way
1:02:00 starting phase (sine versus cosine)
1:03:00 arbitrary amplitude and starting phase
1:04:00 at a fixed frequency, sinusoids are all combinations of sin and cosine
1:06:00 raising the frequency by a factory of two
1:06:30 period of a waveform
1:08;00 adding in harmonics: sinusoids of multiples of original frequency
1:10:00 period of the resulting waveform
1:12:00 higher frequencies
1:13:00 setting frequency to halve the sample rate
1:14:00 foldover (frequency equal to sample rate is same as zero frequency)
1;17:00 maximum is half the sample rate. Standard rates are 44100 and 48000


170-02b-apr8.mp4: Meeting 4, April 8, 2021

0:00 review of contract requirements (A and B projects; all do 8 labs;
(C contract does one ninth lab instead of projects)
1:40 incitement: pulse width modulation made from sawtooth waveforms
5:00 spectrum of sawtooth wave
6:00 no perfect sawtooth wave in digital audio
7:30 you can hear a 55-Hz sawtooth wave even if your speakers can't play 55 Hz.
8:30 subtracting two waveforms using the acoustics library objects
10:30 rectangle waveform
11:00 single sawtooth versus difference between two of them
12:00 detuning the second sawtooth
14:00 spectrum of rectangle waves with changing pulse width
15:30 Two Women, Four Voices by Trevor Wishart and waveset repetition
17:30 first two minutes of piece (part 2, Princess Diana)
19:00 pitch correcting voice versus waveset repetition
20:00 recording from microphone to Audacity
21:00 changing the level of the recording
23:00 close-up of waveform of recorded voice
24:00 duplicating entire periods of vocal waveform
25:00 back to original recording, duplicating waveset insted of entire period
28:00 result of duplicating 3 successive wavesets
29:00 Audacity is very powerful - you can run any lisp function on the samples
30:00 stereo and mono soundfiles in Audacity
32:00 making a sinusoid in Audacity
34:00 (oops, mixed it down wrong)
34:00 select both tracks and reselect "mix and render to new track"
35:00 first mixing result
36:00 time-shifting one of the two sinusoids before mixing
37:00 third mixdown, another phase shift, lower amplitude output
39:00 beating between 1000-Hz sinusoid and 1002-Hz sinusoid
40:30 phase difference is changing in time between the two sinusoids
41:00 apparently changing the output's amplitude
41:30 "fundamental formula of computer music" (my private term for it)
43:30 applying the formula to the Audacity example to explain result
46:00 make beating effect by adding two sounds slightly out of tune
47:00 back to Pd, making a short vocal recording using acoustics library
48:00 applying gain to microphone input using "multiply" and "constant" objects
49:00 playing it back straight
50:00 multiply the voice recording by a sinusoid
51:00 sweeping frequency of sinusoid
52:00 try it with a sinusoid to see what happens to spectrum
54:00 This is called ring modulation
56:00 interference effect between two detuned sawtooth waves
1:00:00 For input sounds, you can use "vdelay" instead of detuning to change phase
1:02:00 doubling the perceived pitch by delaying by 1/2 period of a waveform
1:05:00 this is an example of a  filter.
1:07:00 white noise using the "noise" object in the acoustics library
1:08:00 filtering white noise using the "vdelay" object
1:09:00 objects used in the second lab assignment
1:09:45 graphical view of what happens when two sinusoids are added
1:11:00 different phases give different gains
1:13:00 detuning one sinusoid makes the phase difference change in time
1:13:30 120 degree (1/3 cycle) phase difference, same amplitude out as in
1:14:00 what this implies for incoming noise signal
1:16:00 analogy with light: diffraction gratings and oil films on puddles
1:17:30 sound engineers call this a comb filter


170-03a-apr13.mp4: Meeting 5, April 13, 2021

0:00 incitement: paulstretch "effect" in audacity applied to Wilhelm scream
2:00 different quality of sound when stretched out
2:30 pitch comes through but "presence" is lost
4:00 how to fade sounds in and out
4:30 fading is done using multiplication (applying time-verying gain)
5:00 paulstretch on ozzie-harriet laugh track
7:00 cackles at end of laugh track
7:30 cross-fade between the two stretched sounds
9:00 hmm, timing of crossfade is too abrupt
10:00 changing timing of crossfade (alignment and fade times)
11:00 artistic example: Jacqueline George, Just a Market
12:45 historical context
13:30 how to make political statements without being thrown in jail
15:30 coughing sound emerges from crowd
16:30 function of repetition effect in the piece (presaging a later event)
17:30 ending of piece, automatic rifle fire echoes cough
19:00 keeping meanings ambiguous
20:00 genre is soundscape composition
21:30 more specifically narrative soundscape composition (Yvette Jackson's term)
23:00 preparation in the piece is a kind of repetition
24:00 what happens when a sound comes back in a piece later in time
25:30 what to start with (be clear on purpose, or maybe do the exact opposite)
27:30 the opposite approach: Eno and Schmidt's Oblique Strategies
31:00 theory and technique: more on filtering
31:20 preparatory aside: recording level and gain stages.
31:40 saturation (clipping)
32:30 dynamic range of a signal
33:00 bottom of range is (usually) noise floor
33:30 difference between normal speech level and background noise
34:00 sound being recorded should be well above noise floor
35:00 top of dynamic range (loudest signal achievable)
35:45 signal to noise ratio, in dB.  Dynamic range of human hearing is 100dB
37:00 stages of conversion, each (ideally) with a variable input gain
38:00 even though we're now streaming, it's also a form of recording
39:00 clipping at input of interface and its noise floor
39:30 aligning dynamic range windows at two stages of conversion
41:00 find the stage with the smallest dynamic range
42:30 easy way to line these up is to measure or set headroom
44:30 if you clip or get too much noise there's no easy way to fix later
44:45 not a good strategy to go looking through things on the web
46:00 microphone placement
47:30 getting the mic close to the source improves dynamic range of recording
49:00 try this experiment with your phone
50:00 back to incitement: time stretching using the acoustics library
52:30 this is an impoverished time stretcher, but OTOH it's real time
54:00 filters in the acoustics library
55:00 the low-pass filter ("lowpass" object)
56:00 spectrum of low-pass filtered noise
57:30 frequency response (gain as a function of frequency) of a low-pass filter
58:00 0 dB gain at low frequencies, and a settable rolloff frequency
59:00 band-pass or resonant filter: center or resonant frequency
59:30 gain at center frequency (peak gain), not always 0dB in practice
59:45 a 0 dB gain is a "unit gain" (0 dB is unity).  Linear ("RMS") gain is 1.
1:01:00 bandwidth of a band-pass filter
1:02:00 "Q" ("quality") of a bandpass filter.  Q of zero means no filtering
1:02:40 Q is defined as (center frequency) divided by bandwidth
1:03:00 why we use "Q" as a measure of filter bandwidth
1:04:00 band-pass filter with center frequency 1000 Hz, Q=10 (bandwidth 100 Hz.)
1:05:00 watch out when you decrease Q with speakers open
1:05:30 set level with Q=0, then increase Q if you want.
1:06:00 what Q=100 sounds like
1:06:45 filtering a sinusoid
1:08:00 using "meter" object to measure output level as function of frequency
1:08:45 band-pass filter applied to sawtooth at 2 Hz.
1:09:00 what a 2-Hz. sawtooth sounds like
1:09:30 sawtooth at 2 Hz through a bandpass filter with  Q = 100 or 1000
1:11:00 recording of bandpass output.  Exponentially decaying sinusoid
1:13:00 Ozzie-Harriett-laugh through band-pass filter, Q=10
1:15:00 filtering output of paulstretched laughter
1:16:00 making a major chord out of it
1:17:00 band-pass filters can impose pitches on recorded sounds


170-03b-apr15.mp4: Meeting 6, April 15, 2021

0:00 incitement: feedback as oscillator
1:45 need an object to clip the sgnal (control runaway amplitudes)
3:00 any real object will saturate (clip) at some input level 
3:30 clipping changes teh shape of a waveform
4:30 delay in the feedback path
5:00 need a filter in the feedback path
5:30 feedback gain greater than one causes unstable feedback
6:00 "between" object does the clipping
7:45 talking into the feedback patch
8:30 center (peak) frequency of bandpass filter affects pitch of the output
9:00 higher value of Q makes the system more selective
9:30 tuning fork to inject sinusoid into the system
10:00 tuning fork fights with circuit over which frequency to resonate at
11:00 adding extra delay (to whatever delay the system already has)
12:30 example of this in popular music: 
13:00 (you heard the feedback example through the mic only)
13:30 Forbidden Planet soundtrack example
15:45 soundtrack is both music and sound effects (usually thought of separately)
16:20 movie soundtrack composers have more freedom than pop musicians
18:00 feedback patch makes similar sounds but the technology was different
19:00 example: guitar intro to "it's all too much" by the Beatles
20:30 filtering by guitar strings and electronics; delay was through the air
22:30 Jimi Hendrix at Woodstock
23:30 Jimi reaches for the wahwah pedal (resonant / bandpass filter)
24:00 clippnig is in vacuum tubes in amplifier; delay is physical distance
25:45 software oscillators work usnig feedback in the code
26:30 analog oscillators also work via feedback
26:45 analog synthesis example: Wendy Carlos, Switched-on Bach
29:00 voltage-controlled synthesizer controlled by clavier (music) keyboard
30:00 oddness of idea of maknig a popular record album out of very old music
32:30 same techniques are available digitally
33:00 basic sound source is sawtooth wave and its relatives
34:30 filtering a sawtooth wave
35:30 aside: typing into mumber boxes in Pd
36:00 filtering the sawtooth wave usnig "bandpass" object
37:00 sweeping the filter with Q=10
38:00 lower values of Q
39:00 interesting idea: controlling resonant frequency with an audio signal
40:00 using a multiplier to scale output of the controlling sawtooth
41:00 you can turn the sound off by setting filter center freqency very low
41:30 displaying output of controlling sawtooth generator
43:00 making repeated notes by filtering
44:30 multiple sawtooth generators to make richer sound
45:30 octave is a ratio of 2 to 1 in frequency
45:45 musical interals are set by ratios between frequency
47:00 sawtooth generators in the ratio 1:2:3:4:5 in frequency
47:30 3:2, 4:3, 5:4 ratios as intervals
48:30 shift key while making connection to make multiple connections at once
49:00 the five together sound ambiguously like one or several tones
49:30 spectrum of teh sum
50:30 spectrum of two sawtooth waves in ratio 5:2
51:00 when do you hear the combination as a single pitch?
52:00 detuning teh 5:2 ratio
53:00 fact that 5th, 10th, etc partials are changing draws attention to them
54:00 fixed spectrum graph to agree with audible output
54:30 detuned combinations of waveforms, popular technique in analog synths
55:30 detuned sum into time-varying resonant filter
56:00 clavier keyboard controlling filter using transient (envelope) generator
57:00 another voltage output controls frequency of oscillators
58:30 this is called subtractive synthesis
59:00 music 171 will take this further
1:00:00 acoustics library doesn't do feedback (for the sake of simplicity)
1:01:00 detunig frequencies occur automatically if we use Western musical scale
1:02:50 terminology: harmonic and inharmonic spectra
1:03:30 usnig a filter with very high Q to isolate individual sinusoids
1:04:30 discrete versus continuous (noisy) spectra
1:06:00 harmonic versus inharmonic discrete spectra
1:07:00 spectrum of a bell sound
1:08:00 unevenly spaced components (sinusoidal frequencies in spectrum)
1:09:00 using a filter to examine spectrum of the bell
1:10:30 heard pitch is that of a 141-Hz. sawtooth (this is at the wrong speed)
1:11:00 392 Hz. found frequency is not a multiple of 141.
1:11:30 171 Hz. about a minor third above heard pitch
1:13:00 there might be beating pairs of components in bell
1:16:00 open question, how to make spectra that sound like well-designed bells
1:18:00 idea: use a sinusoid to change the frequency of a sawtooth
1:19:00 even-numbered components are moving in parallel
1:19:30 your ear then hears two sawtooth waves as separate sounds
1:22:00 components can be close to each other and beat
1:23:00 most components of circular bells are in pairs that are slightly detuned


170-04a-apr20.mp4: Meeting 7, April 20, 2021

0:00 incitement: real-time time reversal using the acoustics library
1:00 variable delay time makes Doppler shift
2:00 vibrato from time-varying vdelay using sinusoid to control delay time
3:00 different from vibrato by controlling the oscillator
4:00 variable-delay treatment of incoming sound
7:30 very deep pitch shifts, even making frequency go negative
8:45 diagram shoing how variable delays change frequency
10:00 extreme case where signal flips around backward in time
12:30 voice into extreme vibrato so that it reverses in time
13:00 using a sawtooth wave (instead of sinusoid) to control delay time
13:30 shifting downward only
14:30 real-time reversal of incoming signal
17:00 example: radiohead, everything in its right place
20:30 example: Hendrix guitar solo from Purple Haze - speed doubling
23:30 manipulating expectation in time-based art
26:30 prolongation: doing something later than expected
27:00 prolongation in pop lyrics
28:00 example: Arlo Guthrie, Pickle
32:00 example: Billie Eilish
35:00 another thing about Eilish phrase: loudness balance
36:00 balancing amplitude didn't balance loudness at all
36:45 10-ish decibels is not a 10x difference in loudness
37:00 equal loudness contours
38:00 axes in plot: dB versus frequency (both log scales)
40:00 how loud does a 100-Hz tone have to be to balance 80 dB at 1000 Hz?
41:00 hearing and voice seem to have co-evolved
43:00 threshold of hearing
43:30 loudness differences more perceptible at low frequencies
45:00 need much more sound pressure at low frequencies for same loudness
46:00 spectrum of Eilish voice: peak around 300 Hz.
49:00 tone right after vocal phrase, 50 Hz.
51:00 need 15-ish dB more at 50 Hz. to match 300 Hz.
52:00 the 50-Hz. tone was as strong as apparently permitted
54:00 clarification from last time: harmonics, overtones, partials, components
55:30 periodic waveforms
1:00:00 why we care about theories of loudness
1:00:30 non-definition of "timbre" of a sound
1:02:00 how ears work (very crude caricature)
1:02:30 the cochlea
1:03:00 basilar membrane and nerve cells that fire in time with its motion
1:04:30 why the filtering done by the basilar membrane is important
1:05:30 sounds of different frequencies travel different distances down it
1:07:00 the lower the frequency, the further it gets
1:08:00 typical spatial curves of excitation along basilar membrane
1:09:00 excitation at fixed location as function of frequency
1:10:00 different locations get different frequency responses
1:10:45 graph: Slaney Audio Toolkit estimate of basilar membrane excitation
1:12:00 implication: at a fixed frequency, there's a rapid drop-off
1:13:00 slightly lower frequencies aren't rejected as well as slightly higher ones
1:14:00 critical bands, bandwidth of frequency response at a point on membrane
1:15:00 within a critical band stuff adds in units of power
1:15:30 more widely separated frequencies contribute more to loudness
1:17:00 pitch acuity for flat versus sharp notes, and soft versus loud tones


170-04b-apr22.mp4: Meeting 8, April 22, 2021

0:00 incitement: sample and hold
2:00 noise as input to sample and hold to control oscillator frequency
5:30 decimation (one form of bit crushing)
8:00 decimating a voice recording
13:00 reasons for using simple ("low tech") techniques
14:00 artistic example: another kind of prolongation from Hitchcock, The Birds
16:30 soundtrack electronically composed (not ordinary bird recordings)
19:00 foreground and background sounds (sound changes when we enter school room)
20:00 children's song builds suspense by repetition
21;00 gathering crows effect reinforced by soundtrack
23:00 how the brain buids connections between senses: the McGurk effect
25:00 you are being made to hear the same sound differently because of image.
27:30 more on psycoacoustics: accuracy of pitch perception
29:30 basilar membrane excitation from an incoming sinusoid
30:00 the just noticeable difference in pitch
31:00 two sinusoids at 440 and 441, inaudible difference
31:30 440, 445 (1 percent) difference was decently audible
33:30 there are ten octaves in the range of hearing
34:30 in ideal conditions we can distinguish about 2000 different pitch values
35:00 how can you hear frequency so accurately given basilar membrane filters?
36:00 one possible answer: right-side edge of excitation curve drops sharply
37:00 the place theory of pitch perception
38:00 the alternate explanation: timing of nerve firings
41:00 pitch perception is one of the miraculous things about human hearing
41:30 another miraculous thing: the dynamic range of hearing
43:00 10 billion to one ratio of power between loudest and softest sound
43:30 another miraculous thing: the coctail party effect
45:30 the gestalt theory of perception applied to hearing
46:30 how the brain makes percepts
47:30 some grouping cues: common features; common fate
49:00 common-fate Gestalt principle in hearing: how partials can fuse into one sound
49:30 applying vibrato to even-numbered partials (idea is from Stephen MacAdams)
51:00 graphing the spectrum
54:30 sound of the odd harminics alone
55:00 you might hear the timbre of the lower tone chain change
56:00 applying vibrato to the odd harmonics only instead of the even ones
57:30 perception of loudness
1:00:00 6 decibels is roughly one notch louder to musicians
1:00:30 musicians use the word "dynamic" to mean "force"
1:01:00 the musical symbols for dynamics (ppp, pp, p, mf. f. ff, fff)
1:02:00 if we consider one "dynamic" as 6 dB, then 36 dB range would suffice
1:03:00 36 dB is 64:1 in RMS amplitude or 4096:1 in power
1:04:00 definition of a sone: experimentally, how loud is "twice as loud"?
1:05:30 the word "level" is code for decibels.
1:06:00 loudness "doubles" if you raise it by 10 decibels
1:06:00 relative loudness in sones is 2 ^ ((L - L1)/10)
1:08:00 ISO definition of loudness in sones: [relative RMS amplitude] ^ 0.3
0:09:00 consider threshold of hearing at 1000 Hz. as a reference loudness
1:09:30 loudness of an arbitrary sinusoid in sones
1:10:30 answer for this example: 8 sones
1:11:00 1000 sones in hearing range (because 100 dB gives 10 doublings)
1:12:00 some uses for sones
1:13:00 how VU meters and sliders are marked off in audio equipment
1:18:30 what does doubling loudness really mean?


170-05a-apr27.mp4: Meeting 9, April 27, 2021

0:00 syllabus change: adding a week on "voice"
2:00 2-part incitement: draw your waveform, and dueling metronomes
4:30 second metronome has period golden ratio times that of the first
6:30 two cycles superimposed so you can't tell which is which
7:30 this is a way to be neither random nor predictable
9:30 this works at different time scales and on the same or different layers
12:00 the music of Harry Partch using special, just-intoned instruments
17:15 Charles Corey describes one of the instruments, the harmonic cannon
20:00 consonant and dissonant intervals
21:00 ranges of intervals: beating; roughness; intervals
22:30 spectrum of sum of two complex harmonic tones
23:30 integer-ratio intervals sound consonant
25:00 partials of combination of tones with rational ratio
26:00 layout of Partch diamond marimba
27:00 six blades on SW/NE diagonals are in ratio of 4:5:6:7:9:11
28:00 NW/SE blades are in ration 1/4:1/5:1/6:1/7:1/9:1/11
30:00 building 4:5:6:7:9:11 scale in a patch
34:00 NW/SE scale
37:00 Partch scale (diamond marimba plus some extra tones; 43 in all)
39:30 what's special about integer ratios
41:00 spectrum of two sinusoids added
42:00 critical band theory of dissonance (roughness) for two sinusoids
43:00 critical bands are about 20% wide above 500 Hz; 100 Hz below it
46:30 discordant combination of 1000, 1050 Hz sinusoids
47:30 smaller than 30-ish Hz gives beating; nastiness kicks in around 10
48:30 difference tones
49:00 setting intervals to avoid roughness among partials
49:30 close together or far apart is OK, but in between sounds "rough"
50:00 200 Hz. versus other tones
51:00 terms: consonance and dissonance
52:00 consonance/dissonance of different ratios
54:30 Helmholz theory of consonance/dissonance
58:00 perfect versus almost-perfect intervals
59:30 1/2 way between 6:5 and 5:4 ratios
1:02:00 building out a scale using consonant intervals
1:03:00 3:2 ratio
1:04:30 music theory and the major triad
1:05:00 triad is 3-note chord with base pitch, plus major third and fifth
1:05:30 names of intervals: 6/5 minor third, 5:4 major third; 3:2 fifth
1:06:00 sound of major triad
1:07:00 how to build a Western musical scale out of triads
1:08:30 a fifth is combination of a major and a minor triad
1:10:00 adding the third triad to give a 7-tone scale
1:11:30 a sour interval in the scale (almost but not a fourth
1:12:00 fourth is 4:3 ratio
1:12:30 sour intervals are particularly problematic in polyphonic music
1:15:00 either the fourth is bad or the fifth is.
1:16:00 splitting the difference to reduce the dissonance
1:17:00 Western major scale is made out of triads with adjustments
1:19:00 scale comes from some combination of innate hearing and culture


170-05b-apr29.mp4: Meeting 10, April 29, 2021

0:00 incitement: feedback delay networks ("FDNs")
9:00 mixing delay outputs back to their inputs
13:00 non-repeating echo pattern
15:30 musical example: ending of Beethoven Hammerklaviersonate - cadences
19:00 dominant and tonic chords
23:00 cadences aren't just playing same chord in parallel (some tones go up)
25:00 the whole sequences of not-quite-cadences
28:00 notes on which "false cadences" land aren't climbing by same interval
30:00 the piece can't just stay on the tonic chord - you need to delay resolution
32:00 music works in the context of expectations raised by previous music 
34:30 what do you get when you reverse that last cadence?
35:30 pulse generator (was used in lab but I forgot to introduce it in class)
38:00 spectrum controlled by one parameter names bandwodth
39:00 pulses in time domain (as graphed in "record" are related to bandwodth
42:00 correction from last time: perfect interval between 5:$ and 6:5 (11:9)
46:00 musical scales
47:00 stacking four perfect fifths on top of each other: 81/64 interval
48:30 9:8 interval: major second
50:00 how intervals are named: unison, second, third etc.
51:30 two "seconds" don't make a perfect third
52:45 it's off by 1.2 percent in frequency, more than just noticeable difference
53:30 the interval from 5/4 to 81/64 (syntonic comma, although I didn't say it)
54:30 practical way of resolving the mis-tuning
55:00 the fourth: 4/3 ratio
56:00 interval from third to fourth note is only about 6% (a second was 12.5%)
57:30 the rest of the scale (fifth onward)
58:00 12% is twice as wide as 6%, so why not stick extra notes between seconds
59:00 why the piano keyboard looks the way it does
1:00:00 punch line: if you want to have a scale starting from anywhere...
1:01:30 (half-step is name of the smaller interval)
1:02:30 western major scale is (2, 2, 1, 2, 2, 2, 1) half-steps
1:03:00 how pitches are named
1:04:00 set a number "h" to the ideal half-step ratio.  h^12 = 2
1:05:00 "h" is 1/12 if an octave, so twelfth root of two.
1:06:00 how many half-steps go in a perfect third?  "fixed" third is 0.8% high
1:07:00 the fifth is 0.1% off
1:08:00 how many octaves in a perfect fifth?  log(3/2)/log(2), about 7/12
1:13:00 perfect third is 14% shy of 4 half steps
1:14:00 number of half-steps in the 81/64 "third" - 8% too much
1:15:30 These h-based intervals are called "tempered"
1:16:00 how the three thirds sound
1:16:00 why are there 12 notes in the Western octave?  Two possible answers
1:18:00 12-tone tempered scale has pretty good approximations of 3/2 and 5/4
1:20:00 idea: divide octave into different numbers of equally spaced pitches


170-06a-may4.mp4: Meeting 11, May 4, 2021

0:00 incitement and artistic example: Lucier, I Am Sitting in a Room
13:30 modes of vibration (in an open-ended tube or in a room)
19:30 process music (a particular spin on minimalizm)
23:30 how the use of space in music is impacted by physical isolation
27:30 what Zoom does to sound
30:30 working toward question of what happens when sound bounces off a wall
32:00 sound bounces off barriers (and off open ends of tubes in a different way)
33:00 microphones don't pick up spatial distribution of sounds
34:00 understanding how sound travels helps you plan recording and playback
36:00 sound pressure variations over space
37:00 sinusoidal plane waves, in space and seen along the direction of travel
39:00 the velocity of air motion in a plane wave
40:30 pressure as picked up at a fixed point in space - function of time
42:00 period of sinusoidal signal related to frequency
43:00 wavelength (lambda)
47:00 formulas relating wavelength, frequency, and period
48:30 speed of sound ~ 1100 feet per second; 1000 Hz. gives wavelength of 1 foot
52:00 time of travel of sound through air
53:30 measures of sound strength - intensity and sound pressure level
53:00 sound radiation in terms of pressure and velocity (scalar and vector)
56:00 power and intensity
57:00 possible units of intensity are watts per square meter
57:30 definition of flux
58:00 intensity (flux across an area) is a vector
59:00 conservation of power implies intensity drops with distance r as (1/r^2)
1:01:00 intensity related to RMS sound pressure: I = p^2 / (rho c)
1:03:00 how wattage relates to sound pressue level
1:04:00 nominal sound pressure level that is considered 0 dB
1:05:00 those equal-loudnes contours are normalized to this level
1:07:00 your ear can't withstand much pressure variation at audible ferquencies
1:08:00 intensity of a plane wave is directed in the direction of the wave
1:09:00 a full description of the sound field at a point would include all directions
1:11:00 how the 3 velocity components depend on complete sound field
1:13:00 measurable sound at a point (ignoring its neoghbors) is only 4-dimensional
1:14:30 implications for recording


170-06b-may6.mp4: Meeting 12, May 6, 2021

0:00 incitement: automatic beat boxer using the bonk~ object
7:00 also using a vocoder (will look at that next week)
9:00 sub-incitement: you can make patches into VST plug-ins
9:30 artistic example: Janet Cardiff, sound walks
23:00 back to plane waves and directionality: plane waves bouncing off walls
23:00 planes of maximum pressure at an instant in time in a sinusoidal plane wave
24:30 what the pressure looks like as a function of time
25:00 sound has no polarization (unlike light)
27:00 aside: how sound travels through the earth (solid, except its core)
30:30 incitement (PhD level) make the "earth" plug-in 
33:00 (back to sound in the air) bouncing a plane wave off an infinte planar barrier
36:00 planes where pressure is not changing and others where air is not moving
40:00 nodes are places where there is no pressure variation
43:00 standing waves in an air column
47:00 plane waves reflecting at an angle
48:00 how to use this to measure combinations of velocity and pressure
48:30 omnidirectional microphones only measure pressure, no velocity
49:00 cardioid microphone design using an omni mic and a small reflector
50:00 (back to plane wave reflection) peak pressure change is at the wall
52:30 cardioid equation r = cos(theta)+1
54:00 demonstration: omni microphone near a reflector
56:00 distance from a mic alters balance between direct and reflected sound
57:00 room acoustics in the modal versus the geometric view
58:00 modes in a room are lower-frequency and more numerous than in a flute
59:00 geometric view focuses on reflection
59:30 modes and nodes in the modal view
1:01:00 directional versus omnidirectional mics
1:02:00 different balances between direct and reflected sounds
1:03:00 recording an instrument (mic placement)
1:05:00 far-field guitar recording using an omni mic
1:05:30 proximity effect (but also distorted; that wasn't intentional)
1:07:00 how a guitar radiates sound idealized as a moving rigid plate
1:08:00 low-frequency sound diffracts around from the back of the plate
1:09:00 so low frequencies are attenuated by cancelation
1:09:30 at higher frequencies there is less attenuation
1:10:00 but if you're too close the low-frequency attenuation is reduced.
1:10:30 the far-away sound is considered the "true" sound of the instrument
1:11:00 the close-up sound emphasizes low frequencies compared to far field
1:12:00 problem in recording: get mic away from instrument but keep a clear sound
1:15:00 emitted sound is more directional at high frequencies than at lows
1:15:30 physics of diffraction
1:17:00 angle at which far-field emitted sound drops off (L sin theta = lambda)
1:18:00 in other words, theta (beam width) is about lambda/L in radians
1:19:30 light wavelengths are much smaller so we see much less diffraction
1:20:00 at 20 Hz you'd need a 500-foot wide emitter for a beam 1/10 radian wide


170-07a-may11.mp4: Meeting 13, May 11, 2021

0:00 incitement: vocoders ("channel" vocoders, not phase vocoders)
5:30 linearity of filter input to vocoder (can superpose two inputs)
6:30 vocal production mechanism: glottis and resonant cavities
7:30 glottis can be thought of as a pulse generator
9:30 fricative consonants result from turbulence, and don't involve glottis
11:00 vocoder models the vocal tract filter
12:00 "whispering" by sending noise into vocoder
13:30 example: Laurie Anderson's "O Superman"
17:00 the "Bell Labs" vocal model and what you can do with it
19:00 modeling the vocal resonator as a tube stopped at one end
20:00 possible standing waves in an air column 
21:00 what happens when the air column is closed at one end
23:00 testing a metal tube as an air column 
25:00 6 inch open tube makes peaks at 1000, 2000, 3000 Hz
26:00 spectrum of 1/2-stopped tube: 500, 1500, 2500, ... Hz.
27:00 open tube wavelengths: 2L, 2L/2, 2L/3, ...
28:00 half-closed tube: 4L, 4L/3, 4L/5, etc.
30:00 a real resonator in enclosed space (hard to hear the effect)
32:30 same thing, using reciprocity (placing mic in the enclosure)
35:00 spectrum of shaker lowered into enclosure (more audible this time)
36:00 spectrum of vocal sounds: resonances
37:00 neutral vowel resonances around 500, 1500, 2500 Hz.
38:00 in human speech, resonator constantly changes shape
39:00 up/down and forward/back vowels
40:00 schwa (neutral vowel) is in middle
41:30 spectral peaks at sinusoidal components
42:00 formants, peaks in the heights of the sinusoidal peaks
43:00 reinforced harmonics in singing
45:00 formants don't necessarily lie on harmonic frequencies
46:00 formants determine the vowel (to a first approximation)
46:30 lowest formant approximates front-back position of tongue
47:00 this can be better analyzed as a Helmholz resonator
48:00 low-frequency peak isn't considered a formant
50:00 higher-frequency formants are less clearly resolved
51:30 problem forming vowels when singing high pitches
56:30 ways real vocal production don't follow the simple model
59:00 high harmonics are less well behaved than low ones
60:00 glottal pulses shaped differently from each other
1:01:00 aperiodicity of glottal pulse train mostly at high frequencies
1:02:30 fricative consonants primarily high freqency
1:05:30 pitch of singing versus speaking not as different as you might think
1:07:30 psychoacoustic effect of repeating a spoken uterance (Diana Deutsch)
1:11:00 whether something is understood as singing depends in context
1:15:00 conundrum: how does singing work in a tonal language?


170-07b-may13.mp4: Meeting 14, May 13, 2021

0:00 incitement: phase vocoder, vocal recording up close
3:00 frozen sound (infinite time stretching)
4:30 how the phase vocoder works: splitting a sound into sinusoids
5:00 abusing the phase vocoder with an input that doesn't obey the model
5:30 the window size controls the available ferquency resolution
6:00 1/10 second window, 4096 oscillators playing the soind back
7:00 how it sounds with a much smaller window
9:00 trade-off, hazy sound from a larger window
9:30 what a shwa vowel soundls like with a very small window
10:45 musical example: voice morphs into swarming bees (Trevor Wishart, Vox #5)
14:30 this used the phase vocoder, part of the Composer's desktop project
16:30 radio announcer up close as a waveform
17:30 near-periodicity during voiced portions (vowels)
20:00 non-periodic "s" consonant
22:30 imitating voiced sounds using pulse generator
24:30 time-domain pulse signal (i.e. pulse train as function of time)
25:00 applying bandpass (resonant) filters
29:00 close-up recording of a single pulse through the filter
31:30 increasing q from 10 to 100 so taht you hear resonance as a pitch
33:30 higher value of q makes resonance (ringing)  last longer
35:00 filter frequency response versus waveform of output (amplitude vs. time)
37:00 why people use "q" instead of just specifying bandwodth
38:30 decay time of response
39:30 decay time is inversely proportional to bandwodth
40:00 so q is (loosely speaking) the number of cycles the resonance lasts
43:00 spectrum and time response for q=1, 10, 100, and 1000
46:00 decaying resonance in the vocal recording in Audacity
49:00 appear to have resonances at 700 and 4000 Hz.
49:30 verifying this using Audacity's spectrum display
52:00 attempt to reconstruct a vowel using pulse and filters
55:00 whether to put filters in series or in parallel
1:01:00 seat-of-the-pants alternative: filters in parallel
1:03:00 vowel shape maintained even if changing the pitch (pulse frequency)
1:03:30 replacing pulse train with noise source
1:06:00 real vocal sounds noisier at higher frequencies
1:07:30 changing the vowel sound - vowel is characterized by formant frequencies
1:12:00 speech (production and understanding) has many practical applications
1:13:00 glottis + air column picture revisited
1:15:00 standing waves inside air column correspond to resonances
1:16:00 each resonance should die out in time between glottal pulses
1:16:30 ... unless relaxation time is bigger than time between pulses


170-08a-may18.mp4: Meeting 15, May 18, 2021

0:00 incitement: Shepard tone
7:00 foldover
8:00 rising instead of falling
10:00 Jean-Claude Risset, Sud: Shepard-like effect using comb filters
13:00 changing the interval between components
15:00 Music example: Charles Dodge, Speech Songs
26:00 resynthesis of Dodge piece
28:00 vocal synthesis compared with phase vocoder: transposition and formants
39:00 historical example: Risset analyzing trumpet tones
43:00 evolution of sound quality in a musical note (Cake trumpet note intro)
45:00 spectrum of trumpet tone changes with dynamic ("force") 
57:00 Frequency modulation as a synthesis technique (FM synthesis)
58:00 the two frequencies (carrier and modulation frequency)
1:00:00 changing modulating oscillator amplitude changes strengths of partials
1:03:00 setting carrier and modulating frequency equal
1:04:00 spacing between partials is modulation frequency
1:04:30 making inharmonic spectra
1:07:00 using two modulating oscillators
1:11:00 applying nonlinear functions to a sinuasoid
1:12:30 why f(x) = x^2 doubles audible frequency
1:13:30 cubic and quartic polynomials
1:18:00 "between" object applies an interesting non-polynomial function


170-08b-may20.mp4: Meeting 16, May 20, 2021

2:00 incitement: partial tracer from Pd help browser, 4.data.structures
7:00 editing the partials in a recorded voice
11:00 historical overview of analog music synthesis
12:00 voltage controlled synthesizers
13:00 Max Mathews's MUSIC, 1957, predates voltage-controlled synths (ca. 1964)
15:00 the Telharmonium (Thadeus Cahill)
18:30 Theremin and Ondes Martinot
24:00 voltage-controlled synthesizers in more detail
29:00 music: Morton Subotnick, The Wild Bull (Buchla; San Francisco)
31:00 sequencers used in Subotnick
33:00 music: Wendy Carlos, Switched-on Bach
36:00 difference between multitracking and tape splicing approaches
40:30 how S-OB upset the boundary between "art" and "pop" music
45:00 workings of voltage-controlled synthsizers
46:30 keyboard for pitch control
47:00 "voltage control" in acoustics library objects
48:00 logarithmic control of pitch in analog vs. linear in digital
50:00 one-volt-per-octave tradition in analog synthesis
52:00 the analog gear exponentiated its frequency control inputs
53:00 module names in voltage-control synthesizers (VC oscillator, etc)
54:30 digital modules usually use linear scales such as Hz.
56:00 to combine two pitch inputs, multiply instead of adding
57:30 keyboard control and notes versus sounds
58:30 ADSR envelope (note shaper)
1:00:00 ADSR output (note: the digital one puts out curves, not line segments)
1:00:30 multiplier replaces VC amplifier
1:03:30 VC resonant filter (bandpass object)
1:05:00 sample and hold
1:06:00 keyboard control (faked from PC keyboard but should be clavier)
1:07:00 keyboard outputs: a pitch and a trigger (1 if down, 0 if up)
1:08:00 connecting keyboard trigger to ADSR
1:10:00 outptut from typical ADSR envelope in analog (made up of ramps)
1:13:00 adding another, slightly detuned VCO
1:14:30 changing Q value in resonant VCO (bandpass filter)
1:15:00 different "keyboards" Buchla vs. Moog


170-09a-may25.mp4: Meeting 17, May 25, 2021

0:00 incitement: making VST plug-ins in Pure Data (Camomile by Pierre Guillot)
1:30 Guillot's demo 11 on Vimeo shows how to edit Pd patches inside a DAW
3:00 the Ardour DAW (unlike Ableton - open source; intended for recording engineers)
10:30 drum pad recording as input
11:00 the Pd plug-in (Pd live patching within VST)
13:00 MIDI units to control an oscillator in Pd
13:30 managing VST parameters in Camomile
14:00 example: changing pitch and amplitude of a sinusoid using VST parameters
15:30 example: "Bedrum" plug-in
17:00 drum pad input through Bedrum patch (Irwin's test recording)
19:00 pointer to IRCAM demo showing collaboration with Irwin
20:00 the Bedrum plug-in inside Ardour (the DAW)
21:30 controlling a VST inside someone else's DAW over the network
25:30 dealing with network latency by running everything inside Irwin's machine
28:00 week's topic: sound art and sound studies
30:30 early progenitor of sound art: Luigi Russolo, the Art of Noise
31:30 introductory paragraph: (apparent) fistfights outside a theater
33:00 Russolo's instrumentrium (new mechanical noise-making musical instruments)
35:30 sounds of Russolo's instruments (Risveglio de una Citta)
38:00 non-electric (Italy in the 1920s)
41:00 later developments in novel musical instruments cosidered as sound art
43:00 Baschet brothers' instruments
44:30 Peter Ablinger and Winfried Ritsch, speaking piano
51:00 Trimpin plays Bach cello suite
53:00 Trimpin falling-water-droplet instruments
56:00 short excerpt showing a robot drumming on an old PC
58:00 sound itself as medium.  example: Janet Cardiff 40-voice motet
1:03:00 Liz Phillips, water instrument, with Joan La Barbara
1:04:00 creating standing waves activated by La Barbara's singing
1:06:00 Liz Phillips, Electric Spaghetti
1:08:00 example of visualizing sound: Chladni patterns
1:10:00 Vivian Caccuri, Ritual - candle flames set in motion by sound


170-09b-may27.mp4: Meeting 18, May 27, 2021

0:00 incitement: leap controller as musical instrument
9:00 crazy pool table ball trajectories
12:30 setup as duo performance with Kerry Hagan at NIME conference
13:30 strategy for controllnig instruments with hand gestures
16:30 intro to lab assignment 9: Heisenberg uncertainty principle
30:30 academic discipline: sound studies
32:00 ownership and attribution of musical sounds
24:00 Graceland album by Paul Simon with musicians from South Africa
34:30 Call Me Al, live in Hyde Park
38:30 songs were written (back in US) after recording sessions
39:30 recordings took place during Apartheid era
42:00 questions raised: appropriation or generosity?
45:00 flute solo from deep in a non-US tradition and style
46:00 Bathiki Kumolo's highly recognizable bass lick
53:00 another sound studies topic: sound recording and reproduction
54:00 Victrola phonograph
56:00 scores, "records", broadcast radio, and social media
57:00 permanance and repeatability of recordings ("records")
59:30 scores as a democratized way of sharing music
1:00:00 cost of physically distributing records and need for centralization
1:02:00 making personal copies of recorded media
1:04:00 broadcast
1:05:00 revenue model for broadcasting
1:07:00 differences between network and broadcasting
1:07:30 new revenue model for internet distribution of music
1:10:00 music itself ("content") subsidiary to network infrastructure
1:13:00 importance to artists of keeping up with changes in distribution
1:13:30 recommended books in sound studies: sound studies reader
1:14:00 Noise, Water, Meat, and Listening Through the Noise
1:15:00 architecture and its implications for music


170-10a-jun1.mp4: Meeting 19, June 1, 2021

0:00 incitement: making a sound installation using Raspberry Pi computer
2:00 four sound portraits, Charles Dodge tribute, built into an old telephone
3:30 getting audio into and out of a Raspberry Pi
9:00 the patch runs autonomously and sings or speaks words using a random algorithm
12:00 musical example: Paul Lansky, Idle Chatter
15:00 audio synthesis: linear predictive coding
16:00 More Lansky: Alphabet Book
18:20 techniques for machine-aided composition (compositional algorithms)
19:00 generating scores from computer algorithms
21:00 score editors versus score typesetting systems
22:00 using lilypond to set a melody from a text file with pitches
23:30 example: computer generated sequence (chromatic scale)
25:00 example: using modular arithmetic to generate circle of fifths
32:30 early compositional algorithms didn't use computer typesetting
33:00 entire computer generated musical peices versus computer as assistant
34:00 example: traveling salesman problem for chord progression (Magnus Lindberg)
37:30 feeding computer-generated pitch sequence to a modular synth
39:30 examples: modular-arithmetic clave
42:00 using the C programming language (a classic programming language)
45:00 why make efficient computer programs?
46:30 compositional algoritms in two workflows: batch or real-time
49:00 real-time text-based systems: SuperCollider, RTCmix, Chuck
50:00 modular example redone as real-time compositional algorithm in Pd
59:00 similarity to Shepard tone
1:00:30 tradeoff between text-based and graphical approaches
1:02:00 stochastic (random and pseudorandom) generators
1:04:00 re-seeding a pseudorandom number generator
1:07:00 typesetting result of a graphical compositional algorithm
1:09:30 back to Lansky.  Sampling with and without replacement
1:12:00 back to generating rhythms: changing time onset values


170-10b-jun3.mp4: Meeting 20, June 3, 2021

0:00 incitement: GEM, Mark Danks and Iohannes Zmoelnig, graphics for Pd
4:00 using amplitude of incoming sound to affect graphics
5:30 drawing a polygon
8:30 bird's beak is three triangles
10:00 acoustical attack detection
13:30 machine learning in compositional algorithms
14:30 data driven algorithms
16:30 perceptrons (1950s?) and back-propagation (1980s)
18:30 old-fashioned machine learning: Markov-chain Bach invention
25:00 order of a Markov chain
28:00 mixture of two Markov chains
32:00 rule-driven algorithms (as opposed to data-driven)
33:30 artificial neural networks (networks of perceptrons)
36:00 learning problem example: XOR
43:00 multiple layers in a neural network
45:30 neural networks as splines (curve or surface fitting)
48:30 example: Michael Lee and David Wessel, training instrumental timbres
54:00 limitation: trying to fit something that isn't deterministic
57:00 Judy Garland voice-controlled saxophone
1:00:00 supervised versus unsupervised machine learning
1:04:30 another example: Sam Pluta's joystick-controlled synth
1:09:00 unsupervised algotrithms: example, speech recognition
1:11:00 autoencoders
1:15:00 machine learning and time series.  Recurrent neural networks (RNNs)