hsc3-0.18: Help/UGen/keyTrack.help.lhs
> import Sound.SC3 {- hsc3 -}
> import qualified Sound.SC3.UGen.Bindings.DB.External as X {- hsc3 -}
> g_01 =
> let s = soundIn (mce2 0 1)
> t = fft' (localBuf 'α' 1 4096) (mix s)
> k = keyTrack KR t 2.0 0.5
> p = poll (impulse KR 1 0) k 0 (label "key")
> in mrg2 s p