What are some alternatives?
When comparing Ableton and Google Music Lab, you can also consider the following products
NanoStudio - NanoStudio is a recording studio for iOS, OS X and Windows.
Splice Beat Maker - Make and share beats in your browser
AudioKit Synth One - Free & Open-source iPhone/iPad Synth 🎹
Ramsophone - A generative art/music machine. (Be sure to refresh!)
Sampulator - Make (and record) beats on your keyboard
Incredibox - Express your musicality, pump it up and chill