have you looked into Bitwig? not free but it seems like a seriously well executed project, I have a mate who disappeared for months after being introduced to the Grid modeI'm running an "experimental build" of Reaper atm. Doing any music stuff on Linux is a total pain.
Actually I'm in uni studying coding, so I might even manage to create something. Dunno if I have time for it anytime soon, as I have so much other stuff going on. The software you are talking about is using some sort of block coding?