This sounds great in theory. I don't have a midi interface, but using the home row is a great idea.

If I install the hosted .deb and run it though, then press a, s, d with a 5 second wait it's fine. If I push them after half a second, so while the previous note is playing, it goes very wrong. Is that supposed to happen?

a (C plays, wait 1 second, C still plays), s (after C finishes D plays, a long time later).

press a,s,d and it's C for about 3 seconds, then D and E together.

Is this just a bug with my desktop environment?