It might be cool if entering notes with a MIDI keyboard/normal keyboard made a quick sound instead of just silently adding the note. Some other tools have this feature, like the midi editor Anvil Studio and the tracker MilkyTracker.
(This was brought up in the PK Hack discord server about a week ago. Not sure how possible it would be to implement, but it is a UX improvement, and Livvy added audio feedback to PK Piano for a reason.)