'Monitor Select' allows you to choose which signals to monitor. Its default position is 'stereo', so it monitors the stereo bus, but you can choose to monitor either of the send outputs or the bounce bus. The L/R meter bars on the right of the home screen show the monitored signal level so it's useful to check levels at various points. There is only one monitor system. There is no separate mute for the monitors - the signal goes via the monitor level knob to both the 2 monitor outputs at the back and the headphones.