I'd like to be able to play mandolin with my hands, drums with my feet, and also choose the current bass note. Currently the closest I can do is reach my left hand over to the piano to play a note, but while this is possible with tunes that are not very notey and/or use a lot of open strings it's pretty awkward:

Instead, I'd like to have some sort of sensors, buttons, or triggers on the mandolin itself. That way it's right under my hands, and it takes away much less from whatever else I'm doing. I think the main candidate locations are:

1. Right hand, above the strings.
2. Right hand, below the strings.
3. Left hand, along the neck.

For (a) and (b), I could see either buttons that you tap with the pick or a little stick you 'strum'. For (b) it could also work to tap buttons with the fingers that aren't holding the pick. I'm pessimistic about finding something that works for (c) without getting in the way, but maybe tiny buttons on the top of the instrument would be possible?

Someone made something like (b) for guitar (the Guitar Wing) though I don't think the buttons are quite where I'd like them:

I'm especially interested in the idea of something you interact with using a pick, since that's what's in my hand already. I want to mostly play mandolin, and then every so often send a MIDI signal.

Is this something anyone has been thinking about? Sensor suggestions?

(Another possibility would be to use the Yocto 3D V2 that I previously used for my pain-in-the-neck tilt hat, mounting it on the headstock and have it sense changes in the orientation of the instrument as a whole.)