What are some alternatives?
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
Ableton - Music production software and hardware.
Splice Beat Maker - Make and share beats in your browser
Sampulator - Make (and record) beats on your keyboard
Airdog 2 - All-terrain, camera drone that follows you in action
NanoStudio - NanoStudio is a recording studio for iOS, OS X and Windows.