I love this. I just chose a random song, so I didn't really play with any specific functionality but I think it's a great idea. If you want any UI design help I know someone. I know a few people really. But I love that you are focusing on the concept first and getting in front of people to test. This is far more valuable (to me) than even something like dualingo. I prefer being entertained when I learn. :)
Songlingo