Hi, I am Emma Wang, the creator of Concerto Pro. I created this App when I first noticed a problem. I found out about the problem when I was preparing for my piano competition which contestants to play a concerto. I tried to find a recording of my concerto to practice with, but it turns out there wasn't even one recording. I had to find another person to play the concerto just to practice everyday. I don't want anyone else to run into that problem.