I've been working on a purely server-sided playable instruments add-on that allows you to play them with your building keys. Unfortunately it requires a lot of sound files.
Once I get the needed models with hands (flute, acoustic guitar, bass guitar, electrk guitar, and keytar) I'll release it. There are a few other instrument models that I'd like to have made but aren't necessary (like an accordion, a stand-up bass, a sitar, and steelpan drums).