202 lines
3.9 KiB
Racket
202 lines
3.9 KiB
Racket
#lang scribble/manual
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@(require (for-label racket))
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@title{Pstep}
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timed, sample-and-hold embedding of values@section{related}
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Classes/Pseg
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@section{categories}
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Streams-Patterns-Events>Patterns>Time
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@section{description}
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Pstep is a "sample and hold" pattern: The value returned by teletype::next:: is held at each value in teletype::levels:: for the corresponding duration in teletype::durs::. This cycling is similar to link::Classes/Ptuple::, in that the current repeat ends when eiher pattern returns nil.
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Pstep measures elapsed time using the thread's logical time. That is, it assumes it will be evaluated only exactly when needed, not before.
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See link::Classes/Pseg:: for a pattern whose value changes like an link::Classes/Env::.
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@section{ClassMethods}
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@section{method}
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new
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Create an instance of Pstep.
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@section{argument}
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levels
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A number, collection, or link::Classes/Pattern:: that returns the levels.
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@section{argument}
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durs
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A number, collection, or link::Classes/Pattern:: that returns segments durations in beats.
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@section{argument}
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repeats
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An integer, or teletype::inf::.
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@section{Examples}
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@racketblock[
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(
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// select a chord and duration and repeat it for a random time interval
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p = Pstep(
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Pbind(
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\ctranspose, [0, 4, 7],
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\note, Pwhite(0, 12),
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\dur, Prand([0.2, 0.4, 0.8], inf)
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),
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Prand([1, 2, 4], inf)/4
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);
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Ppar([p, p]).play;
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)
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// change degree independently of number of events that have been playing
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(
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Pchain(
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Ppar([
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Pbind(
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\degree, Pbrown(0, 12, 1),
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\dur, Pstep( Pseq([0.1, 0.2, 0.4, 0.8, 1.6], inf), 3.2)
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),
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Pbind(
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\degree, Pbrown(0, 20, 1),
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\dur, Pstep( Pseq([0.1, 0.2, 0.4, 0.8, 1.6], inf), 4.5)
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)
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]),
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Pbind(
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\scale, Pstep(Pseq([ [0, 2, 4, 5, 7, 9, 11], [0, 1, 2, 3, 4, 5, 6]], inf), 5),
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\db, Pstep(Pseq([2, -2, 0, -2], inf), 0.25) - 10
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)
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).play;
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)
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// use a simple pattern
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(
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Pchain(
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Ppar([
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Pbind(
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\octave, [5, 6] + Prand([0, 0, \r], inf),
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\degree, Prout({ | ev | loop { ev = Pseq(ev[\degree]).embedInStream } }),
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\dur, Prout({ loop { Pseq([0.2, 0.2, 0.2, 0.2, 0.3].scramble).embedInStream } })
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),
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Pbind(
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\octave, 4,
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\legato, 1.2,
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\dur, Prout({ loop { Pseq([0.2, 0.2, 0.2, 0.2, 0.3].scramble * 5).embedInStream }})
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),
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]),
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Pstep(Pbind(
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\db, Pseq([0, -4, -2, -4, -3, -4, -3, -4], inf) - 20
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), 0.2),
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Pstep(
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Pbind(
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\degree, Pfunc({ {10.rand}.dup(10) }),
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\scale, Pfunc({ {rrand(1, 2)}.dup(7).integrate })
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),
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5
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)
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).play
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)
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// change one parameter
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(
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Pbind(
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\degree, Pstep(Pseq([1, 2, 3, 4, 5]), 1.0).trace,
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\dur, Pseries(0.1, 0.1, 15)
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).play;
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)
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// change degree independant of number of events that have been playing
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(
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var a, b;
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a = Pbind(
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\degree, Pstep(Pseq([0, 2b, 3], 1), 1.0),
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\dur, Prand([0.2, 0.5, 1.1, 0.25, 0.15], inf)
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);
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b = Pbind(
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\degree, Pseq([0, 2b, 3], 1),
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\dur, 2,
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\ctranspose, -7
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);
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Pseq([Event.silent(1.25), Ppar([a, b])], inf).play;
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)
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// test tempo changes
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(
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var a, b;
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a = Pbind(
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\degree, Pstep(Pseq([0, 2b, 3], 1), 1.0),
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\dur, Prand([0.2, 0.5, 1.1, 0.25, 0.15], 9)
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);
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b = Pbind(
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\degree, Pseq([0, 2b, 3], 1),
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\dur, 2,
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\ctranspose, -7
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);
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Ppar([a, b], inf).play;
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)
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SystemClock.sched(0, { TempoClock.default.tempo = [1, 2, 3, 5].choose.postln; 2 });
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TempoClock.default.tempo = 1.0;
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// timing test:
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// parallel streams
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(
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var a, b, x;
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var times, levels;
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SynthDef(\pgrain,
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{ arg out = 0, freq=800, sustain=0.001, amp=0.5, pan = 0;
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var window;
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window = Env.sine(sustain, amp);
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Out.ar(out,
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Pan2.ar(
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SinOsc.ar(freq) * EnvGen.ar(window, doneAction: Done.freeSelf),
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pan
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)
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)
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}
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).add;
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times = Pseq([3.4, 1, 0.2, 0.2, 0.2], inf);
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levels = Pseq([0, 1, 2, 3, 4], inf);
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a = Pstep(levels, times);
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b = Pbind(\instrument, \pgrain, \octave, 7, \dur, 0.12, \degree, a);
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x = times;
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Ppar([b, Pset(\mtranspose, 2, b) ]).play;
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b.play;
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r {
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var z = x.asStream; // direct times
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0.5.wait;
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loop {
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z.next.wait;
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s.makeBundle(0.2, {
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Synth(\pgrain, [\freq, 3000, \sustain, 0.01]); // signal tone
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})
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}
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}.play(quant:1)
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)
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::
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]
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