Last night for the opening of the 50th annual Three Rivers Arts Festival, they were serving funnel cakes, kettle corn, gyros, quesadillas and a little dish, served hot, called blues sludge.

It came courtesy of Akron's two-man wrecking crew The Black Keys, holding down the hipster slot on the Arts Fest lineup. It was a return gig for singer-guitarist Dan Auerbach and manic drummer Patrick Carney, who rocked the Friday night set last year at the American Eagle festival.

It was another packed crowd -- I'll guess in the 4,000-5,000 range -- watching the Keys play on the festival stage, now situated in the northeast corner of the renovated Point State Park. Because the grade goes down a bit from the stage, it made for tougher viewing. That, and there's a lot of tall people in this town.

Auerbach and Carney drew from all five albums, pounding out some of the heaviest slabs of Rustbelt blues you'll find anywhere. If you were there last night, it's about the closest you're going to get to the insanely heavy psychedelic riffage of Hendrix.

Auerbach, a true student of the blues, tops it with soulful vocals, especially on songs like "Girl is on my Mind" and "Strange Times," written for the Ike Turner album that never happened.

One potential knock on the Black Keys is that they get kind of same-y over a 75-minute set. A few songs, like "Same Old Thing," meandered too much, sending some folks packing.

It was a mistake to leave, as the Keys saved the best for last with a set-closing one-two punch of The Sonics' classic "Have Love, Will Travel" and "I Got Mine," a new original that sounds just as vintage. The duo sent people home with "Psychotic Girl," "Till I Get My Way" and a slew on monstrous blues licks swirling in their heads.