Clicking and holding the activity LED of an instrument could pre-hear the sample or VSTi at C-4 (+base note), on the current channel or the instrument’s default if one is set.
Releasing the mouse or starting a drag should end the note.
Why it would be useful:
browsing instruments without having to second-guess the current QWERTY octave + MIDI keyboard octave
selection and pre-listening of instruments in one click
gives the LED more purpose (I like it, but it feels like it should do stuff too)