As someone into both music production and retro gaming, my experience of MIDI is that the instrument types are standard but the fidelity and quality of the music varies depending on the samples used. While low-end 90s sound cards had small sample ROMs and better cards had larger sample sets (2 or more MB). More recently there are even larger, very high quality MIDI sample sets which are open source. Also, is General MIDI 2 supported? How about extensions like Roland GS and Yamaha XG?

This is (pun intended) music to my ears!

Then I saw the instrument / note grid, and the keyboard UI - this looks fun!