I want to use music in my server?

I have an online gamming server (Team Fortress 2) located in Chicago and have some sounds people can play by typing a work these sounds are 8 to 20 seconds each, but I would like to put full songs on there for my admins to play when they want.
I have done some research on copyrights and know that it takes 70 years for a song to be public domain, but if the singer is dead how do I find out if there music has gone public domain? for eg: Scatman John died Dec 3 1999 he wrote the song scatman, how would I find out if that song went public domain?

You can call the royalty companies and they will check for you. There are many such firms in LA, and other cities...