Currently, you can play up to a scale with 3 different pitches with an instrument, that I've found so far. You can use the normal keys, press control and key to go to lower pitch, or press shift and key to go to higher scale. The added pitches with the up and down keys add quite a lot of flexibility. However in order to play mostly any song it would be good to have 5 pitches. The current highest pitch is already very high, so I propose these new pitches be added below the current lowest pitch(accessed with alt-shift, and alt-control).
On another note(I'm sorry, I had to), one can only play one note at once. While this is realistic, it severely limits the complexity of music that can be played. I propose that up to 3 notes be able to be played at once(but not more, for sake of anti-spam).
Unless there is something I am missing, and there are ways to access more pitches, this is a great improvement(only problem is that alt-shift is the default keybind for changing keyboard languages on Windows). As for the multi-note playing, I would rather not alt-bot spam to be able to play chords.