What are some alternatives?
Sampulator - Make (and record) beats on your keyboard
Mubert - Electronic music generated in real-time just for you
BlokDust - Join blocks together to build sounds with this web-based music making app.
Friend Mix - Create group playlists for you and your friends
Keezy Drummer - Make a beat in seconds
Ramsophone - A generative art/music machine. (Be sure to refresh!)