A channel is a path used to transport a signal. Lesson 4, "Editing Audio Regions," demonstrated how MIDI channels transport MIDI signals between your studio's MIDI devices and Logic. Audio channels are similar, but instead of sending MIDI messages to a synthesizer, audio channels transport sound to and from your audio interface's outputs and inputs.
Audio channels can also be used to move audio around inside Logic. Busses, which transmit audio from Object to Object inside Logic, are channels. Audio tracks are also channels, but a very special type that reads audio files off the hard disk(s) and sends them to an output or records audio files from an input and saves them on your hard disk(s). To see an overview of the audio channels available on your system, check out the Audio Configuration window.
The types of channels that may appear for your system include the following:
Inputs Input channels represent the physical audio inputs of your audio interface.
Tracks Track channels record audio to your computer's hard disks and also play back recorded audio files.
Bus Bus channels move sound from channel to channel inside Logic. For example, you can send sound from several channels into the same bus, then insert a real-time effect (such as a reverb) on that bus. This lets you use a single reverb on several tracks at the same time.
Instruments Using any of Logic's software instruments, Instrument channels transform MIDI information into audio signals that are transmitted to your audio interface's outputs.
Don't modify Instrument channel 128. Logic automatically inserts the Klopfgeist synthesizer on Instrument channel 128 and assigns it to the MIDI Click Object. (Klopfgeist is German for "knocking ghost.") If you remove Klopfgeist from Instrument channel 128, your metronome won't make a sound!
Aux Aux channels are similar to inputs but can also receive signals from busses, making them perfect for creating submixes.
Outputs Output channels represent the individual physical outputs of your audio interface.
Stereo Inputs and Outputs Stereo Input and Output channels are stereo versions of the standard inputs and outputs.
Master The Master channel is a global volume control for all output channels.
Working with Plug-ins in the Audio Configuration Window
The Audio Configuration window's primary advantage over other editing windows is that it provides a single page where you can examine the plug-ins inserted into your tracks. But even more important, you can move the plug-ins from insert to insert, either in the same channel or to entirely different channels. This works great in situations where, for example, you realize you need your delay after the compressor, instead of before. Just open the Audio Configuration window and move the inserted plug-ins where you want them.