Adding/removing the band’s instruments

In the Band Settings menu, below the list of instruments, you will find the Add/Remove Instruments button.

After clicking on this button, you’ll be able to toggle instruments on and off.

Note: If you simply want to mute an instrument, you may find it preferable to instead go to the Audio/Mix settings and click Mute for that instrument. The advantages of this are 1) the instrument remains muted for all songs until it is unmuted, and 2) if you have a band preset applied to a song, it does not get turned into a Custom Band.