I am starting a project to create a freely available Karaoke game in which one would sing along with music and have one's pitch measured against the melody of the voice for accuracy. My question is this: in order to implement this system, I will need to be able to distribute a file containing the lyrics and melody of a song to people. I will not be distributing the song itself, and will have a copyright agreement before the download is possible that would require users to own the music for which they are downloading the karaoke files, but I wanted to make sure that this would be acceptable under fair use guidelines.
In summary, I would like to distribute a file that will allow someone to turn a song that they have a legal, digital copy of into a Karaoke-playable game song by downloading a file that would have lyrics and melody to configure the program. Is this legal?