Any time the bus is "touched", ie. has its value set (using "/c_set" etc.), a single impulse trigger will be generated. Its amplitude is the value that the bus was set to.
If the bus is set synchronously no trigger will be generated.
The index of the bus to read in from.
The number of channels (i.e. adjacent buses) to read in. You cannot modulate this number by assigning it to an argument in a SynthDef.
compare with In example.