alt Hacker NewsThat's so cool! I'm glad it inspired you to accomplish what you have been putting off for ages. I do think an alternative and more visual/tactile experience can help some people approach music from a different prospective they might be accustomed to. There's definitely room for improvement. If you have any specific suggestions for your use case please let me know. Thanks for checking it out!
I had a think about it as I was writing that comment, and honestly, all I think you're missing is tap tempo. That's it. I thought that maybe the ability to set a different scale for each of the four different instruments would be cool, but I'm not sure that it wouldn't complicate the UX too much. Tap tempo, though, would be useful and I imagine fairly easy to implement.