Pswitch1 chooses elements from the list by a stream of indices ( which ) and embeds them in the stream. If the element is itself a pattern, it embeds only one of its values for each index, and thus switches between all patterns in the list.
(var a, b;a = Pseq([1, 2, 3], inf);b = Pseq([65, 76], inf);c = Pswitch1([a, b, 800], Pseq([2, 2, 0, 1], inf));x = c.asStream;24.do({ x.next.postln; });)//Pswitch used as a sequence of pitches:(SynthDef(\help_sinegrain, { arg out=0, freq=440, sustain=0.05; var env; env = EnvGen.kr(Env.perc(0.01, sustain, 0.2), doneAction: Done.freeSelf); Out.ar(out, SinOsc.ar(freq, 0, env)) }).add;)(a = Pseq([73, 71, 69], inf);b = Pseq([0, 0, 0, 4, 0]+64, inf);c = Pswitch1([a, b, 75], Pseq([2, 2, 0, 1], inf));x = c.asStream;Routine({ loop({ Synth(\help_sinegrain, [\freq, x.next.midicps]); 0.18.wait; })}).play;)