Where do them deeesco-DJ's get the tracks to their "mixes"?

[Niels Mayer <mayer%hplnpm@hplabs.HP.COM>]

I've been wondering about the "art" of makeing them deeesco remixes of
popular songs. In particular, I was wondering if the DJ simply grabs a
record and passes the sound through some arbitrary amount of electronics to
separate the music into different tracks. Or do the DJ's somehow get a copy
of the studio's 4/8/16/32 track master track tape? The former sounds
technically impossible, and the latter sounds pragmatically impossible
because groups generally don't let go of copies of their "source" material.

Please clue me in.

Me? I want to make a deeesco-deathrock-remix of Captain Beefheart's "Bat
Chain Puller" for sonic assault purposes on trendoid deathrock pixies.

-- Niels Mayer.
   (mayer@hplabs.hp.com or hplabs!mayer)