"Queen: Live at the Rainbow '74" Due Out September 9th

BURBANK, CA - JUNE 16: Musician Brian May performs onstage during Queen + Adam Lambert for iHeartRadio Live at the iHeartRadio Theater on June 16, 2014 in Burbank, California.
It's not quite the unreleased music the group has been promising, but Queen has a major piece from its vaults coming on September 9.

"Queen: Live at the Rainbow '74" captures a performance on March 31, 1974 that was recorded for a live album ultimately scrapped when the group finished its third album, "Sheer Heart Attack," in time for release later that year.

The "Rainbow" set will be released in several audio and video formats, including deluxe box sets and some that include a second show from November of that year during the "Sheer Heart Attack" tour. Fifteen of the 17 March songs have never been released in any format before, while portions of the November convert were seen on the now out-of-print 1992 video "Box of Tricks."

The announcement comes as Queen + Adam Lambert is preparing to kick off its North American tour on Thursday (June 19) in Chicago.