Tones.fm is incredibly well done. However I suspect that, compared to this, the additional complexity creates a bit more hesitation for visitors to actually start playing with it. And the demos, while great, also paradoxically reduce the likelihood that the average visitor will actually play with it (it's more tempting to just listen to the demos and call it a day). Maybe the ideal compromise would start off like Music Grid here, but also have additional features subtly hidden but easily accessible.

Discussed at the time: https://news.ycombinator.com/item?id=16552777