hey man! this is pretty neat. it's pretty basic (it was lacking the 15th note for me to make it a full 2 octaves, and each note duration is standard) but it allows you to create a song nonetheless. my kid wasn't looking on and wanted to play with it. here's my song that I composed within 30 minutes:

https://musiclab.chromeexperiments.com/Song-Maker/song/5633105964564480

now to tag a few friends - @calvinlee, @stephhchia, @maxyong!