making an application like that is easy as-long as you have someone that has all the lyrics typed out already
other then that i am sure you would need some sort of copyright licenses to post that information on your own site. i just foresee some sort of infringement there.
any app is possible just not sure what you want totally.
if you need someone to team up with and if this will be a paid project check out my website and i could have the app working in a few days once i know the specs.