TORONTO -- Just as one famous pair of rock 'n' roll lips was flapping in Boston last night, another was at work at the Molson Amphitheatre.

That mouth, of course, belonged to one Steven Tyler, who along with his band Aerosmith seemed driven to knock out a set that, performance-wise anyway, would have given his old heroes a run for their money.

Okay, so tired -- albeit irresistible -- Stones comparisons aside, Aerosmith did more than justify their own legacy. They proved that after three decades and an unchanged lineup, they remain a vital live rock force.

It probably warrants mention that Aerosmith have basically split into two entities: There's the glossy, power ballad-wielding brand name we've heard on record since their late '80s comeback -- something some of us could have done without.

Then there's Aerosmith the performers, a snide and swaggering blues-rock combo content to give audiences a taste of how it all started in the first place. Thankfully, the near-capacity crowd of about 15,000 saw more of the latter last night.

With latest album Just Push Play now over a year old, the band -- which also includes guitarists Joe Perry and Brad Whitford, bassist Tom Hamilton, and drummer Joey Kramer -- were safe to ease off on the promotional kick and weigh in early with some of the best moments from their back catalogue.

That meant that Tyler, having done away with his trademark tights and instead decked out in trendy punk bondage pants and motorcycle jacket, could fire it up with the classic Toys In The Attic, followed in quick succession by Back In The Saddle and Same Old Song And Dance.

Sweet Emotion was also doled out early when the well-preserved Tyler was still in top voice. In keeping with current schtick, the band was hustled out to a small stage on the lawns for a clutch of tunes that featured Dream On -- a novel diversion despite the notable dive in sound quality.

But then, the fact that Aerosmith rocked effortlessly on all those tunes wasn't as surprising as their ability to drop in hits like last year's Jaded and even Dude Looks Like A Lady and have it come off like pure logic.

The right live approach can do a lot to close gaps in quality. Much of the credit for that should go to Perry, whose touch was casually brilliant even on the weakest of songs.

Tyler didn't show signs of fading 'til near the closing encore version of Walk This Way with openers Kid Rock and Run DMC. All told, it was a better Aerosmith than the one that came through here five years ago on their Nine Lives tour. They're plainly still in the game.

Tyler did have to hand over his title of sleaziest rocker to opener Rock.

Following a brief but hit-packed stint by Run-DMC -- during which the veteran crew were openly amused at being the hip-hop odd men out -- Rock made Aerosmith look like a high-class elder statesmen with his hour-plus stack of roadhouse rock, southern boogie, a modicum of rap and whatever else he could chuck at the crowd.

It couldn't miss, though a Detroit medley that fused Bob Seger's Old Time Rock And Roll and The MC5's Kick Out The Jams was particularly inspired.

JAM! Rating: 3.5 out of 5