It's been more than 40 years, but you still hear some fans talking about the "surprise" concert The Rolling Stones held over two days at the El Mocambo back in March 1977. For decades, it's been the stuff of legend and for the most part, only those who were there can really claim to have heard it. 

But soon, everyone else will be able to. The Stones have confirmed that their once "hush hush" Toronto club date is being released as an album, and will be available in all the usual formats.

Even in those pre-Internet days, keeping it a secret was a Herculean task. How did radio legend Duff Roman and others pull it off? 

"Secrecy was paramount in order to pull off the surprise gigs at the 300-capacity club. Booker Dave Bluestein achieved the misdirection by booking Canadian blues-rockers April Wine at the venue on both nights, sharing the stage with an "unknown" band called the Cockroaches."

"Fans entered a radio contest to win tickets to see April Wine. Promoter Duff Roman and the Stones handpicked the winners, who were informed of the surprise while riding a bus to the show. They were funneled in the back door of El Mocambo to avoid drawing any unnecessary attention to the scene."

The album will be out on May 13th and it would not surprise me if Q-107 starts running it as soon as they can get their hands on it. 

Rolling Stones Announce "Live At El Mocambo" Album