Basically, animated items that can play music loops when used. To do this, you would type "/playsong [(beginning of) name of music loop]" to pick what you want to play, then hold primary fire. By default, "none" would be selected. With no music selected, no sound plays, but the instrument continuously animates as if you're playing. Groups of players (or bots) could pretend to play in bands by having just one actually play the music while the others animate silently. Larger instruments might not make as much sense to be running around with, but a few could be made more plausible with straps.
Possible instruments (and associated animations):
- Accordion (squeeze and pull)
- Banjo (strum)
- Bass drum (hit each side with mallet alternately)
- Boombox (not really an instrument but fits with this idea; pulsates cartoonishly)
- Cello (bow)
- Clarinet (bell pulses cartoonishly)
- Cymbals (hit together)
- Electric Guitar/Bass (strum)
- Flute (???)
- French Horn (bell pulses cartoonishly)
- Guitar (strum)
- Harmonica (move back and forth in front of face)
- Keyboard (hands move up and down)
- Saxophone (bell pulses cartoonishly)
- Snare drum (do a drum roll)
- Trombone (bell pulses cartoonishly)
- Annoying Orangeet (bell pulses cartoonishly)
- Tuba (bell pulses cartoonishly)
- Upright Bass (pluck; could "cheat" by using same model as cello)
- Violin (bow)
- Xylophone (hit with mallets)
Additionally, the instrument would emit a music note particle effect. This would make it more obvious that a particular instrument is being played, especially if it lacks an obvious animation (such as the flute which may lack animation entirely).
I would volunteer to model and animate a few myself, but I have no idea where I would begin.