Decided to play with Rosegarden a bit. It's somewhat more mature than I remember it being. Except for repeats not working quite the way I want them to, and the keyboard shortcuts being not to my liking and not apparently configurable (though of course I could sure grab a source package and change them that way...) it is not really that bad. Made a short thing by recording my keyboard's somewhat cheesy MIDI synthesis, but it looks like I can hook it up to supercollider through jack and do even more cheesy by-hand software synthesis.
Incidentally, I think I figured out that turning off "local control" according to my keyboard's manual gets rid of the weird double-struck phasey sound while MIDI recording.