hsc3-0.2: Help/UGen/Envelope/done.help.lhs
done src
Outputs a unit signal if the 'done' flag of the unit at `src' is
set, else output zero.
> let { x = mouseX KR (-1) 1 Linear 0.1
> ; e = linen x 0.1 0.1 0.5 DoNothing
> ; o1 = sinOsc AR 880 0 * 0.1
> ; o2 = sinOsc AR 440 0 * e }
> in audition (out 0 (mce [ done e * o1, o2 ]))