The Kyma Language for Sound Design, Version 4.5

Random Events
The next example generates one hundred random pitches with random durations and random placement
in the stereo field. Edit the Sound called 100 uniform random to follow along.
To generate one hundred of these events, we first create a random number generator, and then repeat the
code for the generating single event one hundred times:
| r t |
r := Random newForKymaWithSeed: 52.
t := 0.
100 timesRepeat: [
self
keyDownAt: t s
duration: (r next + 1) s
frequency: 3 c + (r next * 36 nn)
velocity: r next.
t := t + r next].
You may recognize this as a Smalltalk program (the implication being that you can use any Smalltalk expressions
and control structures to algorithmically generate your MIDI events)!
Local variables are declared at the top by placing them between vertical lines. Then a random number
generator is created and stored in the variable r. Another variable, t, which will be keeping track of time,
is initially set to zero:
| r t |
r := Random newForKymaWithSeed: 52.
t := 0.
Next we repeat the statement within the square brackets one hundred times. Each time through, the duration
is set to some random number between 1 and 2, the frequency is set to a pitch between 3 c and 6 c
(not limited to integer note numbers), the velocity is set to a random number between 0 and 1, and the
start time of the next event is set to a random time up to 1 second after this event:
100 timesRepeat: [
self
keyDownAt: t s
duration: (r next + 1) s
frequency: 3 c + (r next * 36 nn)
velocity: r next.
t := t + r next].
To hear the results, play 100 uniform random. Take a look inside the Attenuator to see how
!KeyVelocity is really being used to control stereo placement, rather than amplitude.
Random generates random numbers that are evenly distributed between zero and one. Let’s modify our
program slightly, replacing Random as the random number generator with several OneOverF generators,
one for pitch, one for duration, one for velocity, and one for the next start time:
| rPch rDur rVel rStart t |
rPch := OneOverF newForKymaWithSeed: 52 states: 128.
rDur := OneOverF newForKymaWithSeed: 52 states: 128.
rVel := OneOverF newForKymaWithSeed: 52 states: 128.
rStart := OneOverF newForKymaWithSeed: 52 states: 128.
t := 0.
200 timesRepeat: [
self
keyDownAt: t s
duration: rDur next s
frequency: 3 c + ((rPch next * 36) roundTo: 1) nn
velocity: rVel next.
t := t + (rStart next * 0.5)].
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