Event Channel -1

Decrement the channel number of the selected events.

This is a quick way of changing the (potential) instrument for a given MIDI event. Valuable when working with multi-channel software instruments or external devices.

Assign notes to voices and staffs in Logic Pro — Apple Support

In cases where the division between voices needs to be more flexible, you can separate voices by assigning each voice to a different MIDI channel. This allows voices to cross while still being displayed independently. Notes not assigned to any MIDI channel are not displayed, allowing you to “hide” notes from display (such as improvised parts or trill notes, for example). This does not affect playback, but only the display of notes in the score (the playback channel is determined by the setting in the Track inspector).