I think this is really interesting, seeing where the beats for songs come from and checking out the originals when samples are used...here are 4 of the samples from Eminem's "Relapse," followed by an interview that Em did with one of his former biographers where he talks about "Relapse II" which he plans to release this year.
1) The Skinny Boys: Human Jock Box (from "Insane")
2) Queen & Paul Rodgers: Reaching Out (from "Beautiful")
3) Walter Egan: Hot Summer Nights (from "We Made You")
4) Mike Brant: Mais Dans Ma Lumiere (from "Crack a Bottle")
"It was a relief for me to not worry about the beats and strictly focus on writing and what the hell I wanted to say. It took a lot of the stress off. But "Beautiful" is a different story. That song is the only one out of a whole batch of songs – probably three or four albums' worth of material – that I recorded in the time I was gone. I did all of that when I wasn't sober and that is literally the only song that's on this record. I don't know if any of the others are going to make it to Relapse II, which I plan to release later this year, because I haven't picked out those songs yet."