Music 171 homework 2
Starting in the early sixties, the composer Steve Reich made famous
a technique called 'phasing' in which two loops, almost identical
but of slightly different lengths, are played simultaneously so
that you hear the contents of the loop juxtaposed against itself at
all possible phases. This assignment is to make a simple
phased-loop player using sinusoidal oscillators with wavetables to
control their pitches. You could make your own choice of pitches or
frequencies; the example provided uses this sequence:
990 770 880 1210 1320 770 1320 880
Your successful patch should sound like this, although with perhaps your own more
artistic collection of pitches.
To make the patch (each of the following steps is worth 2 points
for a total of 10):
- make two oscillators (osc~ is fine), preferably one playing to
the left output channel and the other to the right. Their
amplitudes should be turned off and on with a line~ object; you can
use the same line~ to control both.
- make a table with 8 to 20 frequencies (or MIDI pitches if you
prefer). The range of the table should be set to something
reasonable so you can see the frequencies or pitches; 0 to 1000
might be a good frequency range and 21 to 108 might be a good range
for MIDI pitches. Make a message box to stuff the values you want
in the table; but set the table up so that its contents are saved
with the patch or else so that the table-filling message is sent
when you hit the "start" button.
- Make start and stop buttons as before but also provide number
boxes so that we can try changing the tempo and number of notes in
the sequence.
- Make a phasor~ whose frequency is controlled by the tempo
control. .Using a multiplier, adjust the output amplitude of the
phasor~ to equal the number of notes in the sequence (the second
numeric control you made). Connect to a tabread~ object to get an
audio signal to cotrol the pitch frequency of one of the osc~
objects. (If you want pitch control you will beed a conversion
object, mtof~.)
- Add a second phasor~ and tabread~, with the difference that the
phasor~'s frequency has 0.1 added to it so that it runs slightly
faster. Hook output to the frequency input of the second osc~ and
presto.
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