Music 171 homework 7
Psychoacousticians have long been interested in the phenomenon of
streaming, in which a succession of sounds is heard as a single stream,
like a melody or a person speaking. Cues that might contribute to hearing
sounds as belonging to a stream might be proximity in time, pitch, amplitude,
timbre, or physical location, This assignment is to reproduce a famous
experiment of David Wessel (from the paper, "Timbre Space as a Musical
Control Structure", 1979). In the experiment a loop of six sounds is
heard as a single stream if cycled slowly, but as two separate ones if cycled
more quickly. The sounds in the loop could be made by filtering wavetable
oscillators, for instance as shown:
The two timbres should be quite different from each other, although the
sounds of both timbres should have a clear pitch (i.e. they should be
periodic tones). In this assignment you can make them using a fixed waveform
and filtering with "vcf". The illusion works best if the notes are
separated in time, i.e., each one should turn off smoothly and the next one
should turn on smoothly; don't just change the pitch while the note is playing.
To make the patch:
- Make a text object with the six lines shown above (65 75, and so on). Make a
metronome and a counter to access the six locations repeatedly. Make a control
for the number of milliseconds per location.
- Make a wavetable synthesizer with a waveform that contains reasonably
strong harmonics (not just a sinusoid). It should play MIDI pitches taken from
the first column of the text file.
- Convert the MIDI values of the second column in the text file to frequency
and use these for the resonant frequency of a vcf~ object. Set the "Q" to
around 7. Use the resonant filter to filter the waveform you generated.
- Using a line~, arrange for the output of the vcf~ to be ramped down to zero
40 milliseconds before the oscillator frequency and the resonant frequency
change. (To do this, you have to delay the updates of the two frequencies,
storing their values using "float" objects, so that the updates happen after the
line has finished ramping down.) At the same time as the frequencies are
changed you can then ramp the line~ back up over another 40 milliseconds. There
is an example of this in the patch 6.d.more-delays.pd (where the same technique
is used to de-click a delay read; but instead of 10 milliseconds it will sound
better here if you use a slightly longer delay).
- Verify that, if you use a value of 400 for the time between "notes"
(frequency settings), you hear ascending notes grouped in threes, and that
if you reduce the time to 120, the "110" notes are streamed together and
descend. The "75" notes should also descend but they will be harder to focus
on. (If you wanted to work harder, you could make them louder than the "110"
notes to improve your ability to hear that stream separately).
The output at the slow setting should sound something like this and the faster one like this. This assignment should only require submitting one
file. If only one file is needed, you can just upload it without making an
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