Instruments are pretty terrible, devs should just throw away the current system and replace it with MIDI so you could plug some MIDI input thing in your computer and then play music in game. This would allow people to actually play their instruments.
Also add some stationary instruments like piano.
Of course there are a few things to solve, like how to deal with latency etc. But that is for devs to solve, and there are solutions. Other games have done it, why not HnH? It would add a lot of depth to community gatherings etc.