From here:

"New Music: UNKLE [ft. Josh Homme]: "Chemical" [MP3/Stream]

"Chemical" originally appeared on UNKLE's 2007 album War Stories as an instrumental called "Chemistry". However, according to the London sci-fi electro-rock outfit's James Lavelle, Queens of the Stone Age frontman Josh Homme-- who sang on War's "Restless"-- had already come up with a vocal idea for this song but ran out of time to finish it.

Homme's calendar must have cleared up in time for UNKLE's forthcoming fourth proper album, End Titles... Stories for Film, because his croon now hovers over the original string-drenched track. "I'd let nature take control, but it's not possible," he intones. Always a bummer when there are chemicals between us."