Write a signal to a bus.
Note that using the Bus class to allocate a multichannel bus simply reserves a series of adjacent bus indices with the Server object's bus allocators. abus.index simply returns the first of those indices. When using a Bus with an In or Out UGen there is nothing to stop you from reading to or writing from a larger range, or from hardcoding to a bus that has been allocated. You are responsible for making sure that the number of channels match and that there are no conflicts.
The index of the bus to write out to. The lowest numbers are written to the audio hardware.
An Array of channels or single output to write out. You cannot change the size of this once a SynthDef has been built.