freeSelfWhenDone src

Free the synth when the 'done' flag of the unit at `src' is set.

> let x = mouseX KR (-1) 1 Linear 0.1
>     e = linen x 1 0.1 1 RemoveSynth
> audition (out 0 (sinOsc AR 440 0 * e))

> let x = mouseX KR (-1) 1 Linear 0.1
>     e = linen x 1 0.1 1 DoNothing
> audition (MRG [freeSelfWhenDone e, out 0 (sinOsc AR 440 0 * e)])