Hi! I love your program! It has the old 80s sampler vibes.
I have a couple of suggestions:
1) You can make it a VST so the user can use it with his/her DAW (as well as the current standalone application)
OR
1.5) make a bridge vst that sends data from your standalone program to the bridge vst.
2) You can add a feature to import and export .midi files.
3) Make it easier/more clear for the user to know how to access the menu. It's hard to guess that you should click on the project name in order to access the menus. Add a button somewhere for the menu.