An interesting concept, but I think it lacks a lot of polish. I think it could have had a tutorial that started with one track, then added another, and so on. Also, there were times where I wanted to play multiple tracks together to see if I had the right combination of tracks before I committed, but I couldn't, whether by design or not. Also frustrated by the fact that I couldn't stop a track from playing, and had to wait for it to finish.
Also, shorter tracks may help with retention, and I also imagine that having an option for more graphics on-screen might help engage sighted gamers a little more, like soundwaves when a track is playing, or changing colours when you get things right or wrong.
Still, a great concept, and as a musician, I really enjoyed the challenge of trying to pick out the different tracks from the main piece. And this is definitely an admirable goal to make a game for those who may not be able to enjoy the vast majority of video games.