Rolling Stone:  Rock and Roll Daily - 11/6/09, 10:04 am EST

Photo: Diamond/Getty (Swift), Merritt/Getty (Mayer)

Another track off John Mayer’s Battle Studies has leaked before its November 17th release date: “Half of My Heart,” a duet with Taylor Swift. The pair team up for a nice piece of Fleetwood Mac-inspired pop in which Mayer sings, “Half of my heart is a shotgun wedding to a bride with a paper ring, but half of the heart is the part of a man who hasn’t truly loved anything.” Hit up Perez Hilton to listen to a stream.

If the track has a flaw, it’s that Swift’s appearance is, well, too swift. The track will no doubt be in constant rotation for fans of Mayer, Taylor and Rumours. Also, there’s no opening references to getting stoned, so radio should like it, too.

Swift will be this weekend’s Saturday Night Live host and musical guest.

Look back at Taylor Swift’s rise to stardom.

“Half of My Heart,” track three on Battle Studies, appears on the brighter side of Mayer’s new LP, as the guitarist recently told Rolling Stone, “The record starts out sort of like the sun is out, then it gets darker. And then the sun comes back out at the end.” “Half” also seems to avoid all the combat metaphors featured on Studies. “I was loving the war theme, the battle theme. The militaristic, vulgar, violent side of a relationship on the down slope,” Mayer told RS.

Mayer has already charted out a plan of attack for his 2010 tour, so check out the Battle Studies dates here.