Send different parts of your signal to different hardware outputs - for example, your guitar to the PA and your practice track to your headphones, or keys and guitar to separate amps.
By default, everything is mixed to a single output pair. Multi-output routing is optional and off by default, and your settings are remembered.
Guitar
Each source can be assigned to its own output pair on your interface.
A single audio interface with enough output channels (more than one stereo pair)
Normal output mode - multi-output routing is not available in Split I/O mode
If your interface doesn't have extra outputs, the routing options won't appear.
Open Settings (⌘,) and go to the output routing options
Turn on the separate-output option
Assign each source - Guitar, Keys, Practice Track, Metronome - to the output pair you want
Changing a source's output pair is seamless - your plugins are not reloaded, and audio keeps playing
Turning routing on or off, or switching your audio device, may briefly rebuild the audio engine
Your routing is saved and restored on relaunch
If a saved output pair is no longer available (e.g. you unplugged that interface), audio falls back safely to a working output instead of going silent
Your guitar chain (and any backing audio)
Keys
The Keys Mode instrument chain
Practice Track
The practice/backing player
Metronome
The metronome click