How do you remove the singers voice in a song so its just the backround music?

I want to be able to like sing a long to a song on one of my CDs or ipod so i cant hear the singer but i can still hear the backround music? so its like karaoke? Any body know how to do this? i have a elaborate sterio, im getting an ipod touch soon- but i have an OLD ipod right now, i have a CD player? any ideas how i could do this?