Trivial MIDI editor suggestion:

Shift-click on key in piano roll = select all notes with that note value. When messing with drum parts, it occasionally comes to pass that I realize that there's a way nicer drum than one of the ones I picked. Being able to grab "every C2 note" and move them all at once is really handy, and "shift-click C2" is a lot less error-prone than "control-right-drag over the display". (On a Mac, if it matters.)

You can do that with mouse customization. Open Preferences -> Mouse modifiers. In the context fields choose "MIDI note" and "left click". Double click on the modifier key you want to assign (shift) and choose "Action list...". There you find the action "Select all notes with same note value". Highlight it and hit the "Select/close" button. Back in the preferences hit the "Apply" button and you're done.

Thanks! That's very close, certainly. I can't seem to get it to do something in response to clicking on the keys over on the left of the window, but shift-clicking on the row in the piano roll is good enough to make me much happier.

Oh I misread that part, sorry. You can select all notes of a pitch with a right click on those piano keys. Ctrl + right click adds to the current selection, which is a tad weird (in other places shift adds while ctrl toggles). I don't think you can change that to shift + left click.

What's the name in the mouse preferences for "the piano keys", or do they not have one? While I'm at it: Messing around with duplicating a previous setup, I tried changing left click to "just insert a note" in the piano roll, which actually works pretty well, except that it doesn't play the note when inserting it, which is confusing to me.

You can move the notes also with ctrl-down or ctrl-up. I'm sure there is an equivalent key on Mac. :) -Data