LSDJ and emulator, like mentioned above
don't pull your hair out
tracker interface can take some getting used to, and you'll find yourself getting quite angry about your process until you pass that hump and understand the logic behind what it is you are doing (if its even a tracker style app you go with)
and, yeah.... nanoloop is a bit easier to jump into, imo. but less rewarding in the long term (again, imo). learning curve is considerably easier though if you don't have a tracker background. its a bit like playing a game.