tChoose is a composite of tIRand and select.

> import Sound.SC3 {- hsc3 -}

> g_01 =
>     let x = mouseX KR 1 1000 Exponential 0.1
>         t = dust 'a' AR x
>         f = midiCPS (tIRand 'b' 48 60 t)
>         o = let a = mce [sinOsc AR f 0
>                         ,saw AR (f * 2)
>                         ,pulse AR (f * 0.5) 0.1]
>             in tChoose 'c' t a
>     in o * 0.1