Back in 1977, between the ill-fated Black and Blue and the career-rejuvenating Some Girls, the Rolling Stones managed to keep secret, for a little while anyway, their intentions to play a pair of intimate shows at Toronto's famous El Mocambo club. With fans lined up to see local heroes April Wine, via tickets won through a radio contest, supporting act the Cockroaches looked quite familiar once they took the stage.

The Stones played two shows on March 4 and 5 at the 400-seat club, filled with classic songs ("Honky Tonk Women," "Jumpin' Jack Flash"), old favorites ("Route 66," "Little Red Rooster") and some new cuts ("Worried About You," which wouldn't surface until four years later on Tattoo You). Four songs from the concerts showed up on the concert album Love You Live that September, buried among bloated tracks taken from the road-weary band's 1975-76 tour.

Those songs were always the standouts on the live LP but haven't been heard in their proper context (at least legally) for more than 45 years. Live at the El Mocambo gathers the entirety of the March 5 performance along with three songs from the earlier show, and it's a revelation for anyone who thought 1978's Some Girls was the trigger point for the Stones' return. All they needed, it turned out, was to get out of the spotlight and back to their roots to reclaim their crown as the Greatest Rock 'n' Roll Band in the World.

Of course, Some Girls confirmed this as the group confronted its looming dinosaur status by going on the defense against punk and disco, adapting the young genres to their strengths and needs. You can hear them already thinking of this approach in El Mocambo's 23 tracks, reworking old classics by injecting new life into them. Mick Jagger snarls, Keith Richards and Ronnie Wood's guitars slash and Charlie Watts and Bill Wyman's on-point rhythm forcefully pushes everything along.

The set list is mostly familiar; many of the songs were staples of their world-conquering tours from the previous half-decade or so: "Tumbling Dice," "Let's Spend the Night Together," "It's Only Rock 'N' Roll" and "Brown Sugar" have been part of Stones shows since they were introduced. What's different here is the band's looseness. Early on they go through the motions for the most part, but once they settle into the smaller stage and an audience that's an integral piece of the performance it's easy to forget they were filling stadiums just months earlier.

So the middle section of the 107-minute album is the launching point of the show's legend. Starting with mid-set covers of Muddy Waters' "Mannish Boy" and Bo Diddley's "Crackin' Up" and ending with a one-two punch of "It's Only Rock 'N' Roll" and a breathless "Rip This Joint," the Stones hadn't sounded this vital onstage since the '60s ended. Check out the snapping "Around and Around" and the way they raunch up the already raunchy "Star Star." And "Little Red Rooster," a Love You Live highlight, takes a similar central position here.

But even the overplayed and relatively weaker tracks come alive in the new context. A minor song like "Hand of Fate" from Black and Blue crackles with energy here, as Jagger and Richards share a call-and-response near the end. The often-played "Jumpin' Jack Flash" doesn't sound like an obligation, as it has onstage for years before and since this Toronto date – especially in the go-for-broke finale. Whether intended or not, the performances heard on Live at the El Mocambo gave the Rolling Stones the jolt that they needed to move forward during a period of doubt. It was another turning point, finally available for all to savor.

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