there are a number of multi track "session files" floating round on the net...not many modern ones though.
So far i've found
Christina Aguilera - Genie in a bottle
Marvin Gaye - Ain't Nothing Like The Real Thing
Marvin Gaye - Mercy Mercy Me
Marvin Gaye - Whats Going On
Marvin Gaye - Grapevine
Marvin Gaye - AintNomountain
Bob Marley - Is This Love
Bob Marley - Lively Up Yourself
Bob Marley - No Woman No Cry
Queen - Bohemian Rhapsody
Stevie Wonder - Superstition
I've got some more I can bothered typing, like nirvana, bare naked ladies, and some old beatle 4 tracks. They're around you just gotta search, here's an example of where I would start
http://www.google.com.au/search?hl=en&q=Bob+Marley+-+No+Woman+No+Cry+multitrack&meta=
google the artist , song name and the word multitrack
There's a good chance the one you want isn't around in multitrack form, so then as already mentioned, filtering is your best option. Or replaying the sample.