xOut bufferIndex xFade inputs
 
Send signal to a bus, crossfading with existing contents.

> let { p a b = sinOsc AR (mce [a, b]) 0 * 0.1
>     ; x = mouseX KR 0 1 Linear 0.1
>     ; y = mouseY KR 0 1 Linear 0.1 }
> in audition (mrg [ out  0   (p 220 221)
>                  , xOut 0 x (p 330 331)
>                  , xOut 0 y (p 440 441)
>                  , out  0   (p 120 121)])