Meet 2004's answer to AC/DC. Sam Roberts may be younger, hairier and more painfully earnest than Angus Young and company. But had it not been for a last-minute save by Sloan, he would have completely stolen their show out from under them on Saturday (albeit on a considerably smaller scale), much the same way AC/DC did to the Rolling Stones at last year's SARSstock. And even as it was, he came awfully close.

One-day music festivals are funny things. Audiences jump through sizeable hoops to get to them (in this case hopping aboard a ferry and heading out to Toronto's Olympic Island), then spend most of their time doing their best to ignore the on-stage talent - generally by retreating to the beer tent for the unique pleasure of lining up for hours for $6 cans of Canadian (for the less ambitious, lying on their backs in front of the stage and trying to catch some zees will suffice). Then, sometime around dusk, they realize they're supposed to be at a rock concert and emerge looking for a little action - and if whoever's holding a guitar at that particular moment is up to it, the show is theirs for the stealing.

Roberts was just the man for the job. With only one album under his belt, he's already reaching Tragically Hip territory - a virtual unknown outside our borders, but a genuine rock hero within them. As an added bonus, he also has a bit of sex appeal - as evidenced by the afternoon's constant stream of young women toward the VIP tent in search of autographs, and the peculiar spectacle of bearded look-alikes being mistaken for the man himself and politely posing for photos.

Even opening with the underwhelming Taj Mahal, a psychedelic misfire from last year's We Were Born in a Flame, wasn't going to put a damper on things. Nor was the challenge of transferring an act that plays best in sweaty concert halls to an idyllic meadow within shouting distance of a children's amusement park. Earlier in the day, the Constantines - a notoriously riotous club act - had struggled with that transition; Roberts seemed to thrive on it.

If you can achieve an audience sing-along to the embarrassing Canadian Dream ("S-O-C-I-A-L-I-S-M is here to stay, S-O-C-I-A-L-I-S-M is the only way"), you can pretty well do anything. So when he busted out Don't Walk Away Eileen and Where Have All the Good People Gone?, Roberts had the heretofore passive Torontonians with hands in the air, voices at full pitch and girlfriends aboard shoulders. And if that wasn't enough, we got K-OS turning up in the middle of Brother Down (fresh from a guest stint on the bongos) to offer the day's only rap outside Buck 65.

All this made for an unenviable challenge for Sloan, who had meticulously put together one of the summer's best concert bills - a who's who of Canadian talent that also included Broken Social Scene, the Stills, Pilate and the former Death from Above (now Death from Above 1979, for Charlatans UK/Bush X reasons) - and reserved the headline slot for themselves. By the time Sloan took the stage, concert-goers had already been rocked out by Roberts and were busy contemplating how best to beat the crowd to the ferry docks.

Happily, the transplanted Haligonians - something of a hit-and-miss live act - were mostly up to the task. As though responding to Roberts' challenge, they wasted no time in hitting the sure-fire favourites (Underwhelmed, The Lines You Amend and The Rest of My Life) to hold off an early exodus to the gates.

The headliners had a few built-in advantages over their upstart competition. Nifty lights, for one thing. And, more importantly, a hefty back catalogue that meant they could effectively breeze through a greatest hits package without wasting time on any clunkers.

Still, it took a rousing rendition of Money City Maniacs to lift the band from a mid-set lull, propel it into a terrific encore version of If It Feels Good Do It, and remind all concerned that they could still give Roberts a solid run for his money.

Had enough of the assembled masses been paying attention earlier, mind you, Broken Social Scene might have stolen the thunder from both of them. A late addition to the bill, and thus scheduled improbably early (before Pilate, for crying out loud), the jam-happy collective's brand of controlled chaos proved the perfect mid-afternoon treat. And just in case we couldn't tell how much fun they were having, various members of the 10-member contingent kept on coming back to remind us - drumming with the Stills, bongoing with Roberts, and conga-lining their way through Sloan's Coax Me.

Other acts had a tougher time making their presence felt. Even the highly-touted Stills (spotted, guitars in hand, in line for the island-bound ferry - couldn't someone have sprung for a water taxi?) were only able to win over the assembled throng with the last few minutes of their set. Like the Constantines and others, they'll have to console themselves with their superior cross-border success; domestically, even Sloan isn't safe from the Roberts juggernaut.