Is there something similar to this that includes melody composition that's not tied to a scale? My son has been composing music for a couple years in Chrome Mus

Is there something similar to this that includes melody composition that's not tied to a scale? My son has been composing music for a couple years in Chrome Music Labs and he's definitely outgrown it, but I can't find anything that lives online (and ideally can be downloaded in a single html, love the idea) and allows any-length melodies to be composed within the browser with drumkits, etc... Something like Caustic, but in HTML :-)