Oops, that should have been "the music group I run for adults with learning & physical disabilities ..."

I just remembered a friend years ago had a device that had 6 levers and keys, that went over the strings at the other end, effectively converting the guitar into a 6- string piano- you pressed a key and the lever hit the string. The left hand played as normal.

It sounded quite interesting (a bit like hitting the strings with dulcimer sticks). I'm not sure if it opened up any particular playing techniques that weren't otherwise achievable with the fingers, but it did look very cool.