These are interesting tools. Pitch detector didn't seem to work too well for me but no doubt my bad singing. You could probably just show both clefs with the relevant clef symbol at the beginning rather than making it an option. For the beat detector, it would be interesting to see average distance from the beat in order to try to improve. It could be a game following a rhythm easily.
Think for HN you probably need a quick demo that will attract more of the large number of people who are not necessarily going to use this tool long term. Give people a hook. Also keep trying, because it's pretty random what gets voted up on any one day. I think with some development and innovation this could be a useful tool. You've also not got any contact info which makes it harder for interested people to get in touch if they like your stuff.