In Logic, how do I mute all tracks assigned to the same Instrument?

You want to mute an instrument (ex. bass) throughout an entire song, without opening folders everywhere and muting each track individually. In order to achieve this, you use the “change instrument globally” command. Find one of the tracks with the bass line on it and while holding the Option key down change the bass’s instrument to “No Output”. This will change it in every folder on any level hence muting the entire Bass performance. To un-mute it, do the same in reverse. You can also use this to globally change one instrument to another.

Warning (maybe too obvious, but still…): if you’ve set all bass tracks to ‘No Output’ and also set all piano tracks to ‘No Output’, there’s no way you can globally assign all bass tracks to the bass instrument again (except by dealing with them one by one). Trying to Option-assign the bass instrument would also assign the piano tracks to the bass, since all those tracks are set to ‘No Output’.
Instead of assigning the tracks to ‘No Output’, you could assign them to e.g. different Monitor objects (or some other environment object with no Port setting and cabled to nothing) you created in the environment. Call one Monitor “bass mute” and another “piano mute”, check their icon-checkboxes in the parameter pane so they’ll appear in the Instrument list, and off you go.

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