SuperCollider busses work just like busses in other audio creation contexts, which work similarly to busses used to transport humans. Busses are used to send audio from one place to another, and in SuperCollider they can also be used to send control-rate signals. Each SuperCollider bus is given an index number, which are integers starting at 0. Audio-rate busses and control-rate busses are independent, and are given an independent set of index numbers. Any number of unique signals can be routed into a bus, and any number of receivers can take signals from a bus - but the signal will be the sum of all the input signals. In other words, if you want to send two different sets of signals, you need two different busses with different index numbers.
11.3.11.1. Audio-Rate Bus Numbers
There are special audio-rate busses reserved automatically by the server. These interact with the audio interface, allowing you to get sound from its inputs, and send sound to its outputs. The lowest audio-rate bus numbers are reserved for audio interface outputs, each channel receiving an independent bus. The bus numbers just above those are reserved for audio interface inputs, each channel receiving an independent bus.
For a simple audio interface with two channels each for input and output, the pre-reserved audio-rate bus numbers would be these:
0 for left channel output
1 for right channel output
2 for left channel input
3 for right channel input
Now you can change the first argument of the "Out" UGen as desired!
