It would not be an insult to say that Tom Petty and the Heartbreakers are a "meat and potatoes" rock act.

It wouldn't be entirely accurate, either.

Petty and his hall of fame backing band don't rely on gimmicks or pyrotechnics to put their music across to appreciative audiences like the packed house that witnessed the band's second of two Summerfest headlining gigs Saturday night at the Marcus Amphitheater.

They simply serve up laser-pure versions of their songs, old and new, with off-the-charts musicianship and a cohesion that once prompted Bob Dylan to say that playing with the Heartbreakers was like "playing with one guy."

Meat and potatoes?

Think filet mignon and a side of garlic mashed from Peter Luger or one of the other "best I've ever had" steakhouses.

"Mojo," the Heartbreakers' 12th studio album and the impetus for another summer of barnstorming, is a loose, blues-drenched collection of songs recorded without overdubs.

After opening the night with a handful of hits like "Listen to Her Heart," "You Don't Know How It Feels," "Breakdown," Petty and his backing band -- Mike Campbell (guitar), Benmont Tench (piano), Ron Blair (bass), Steve Ferrone (drums) and Scott Thurston (just about everything) -- served up a four-song slab from the new record that was just as tight as the show-closing "American Girl."

Petty, who turns 60 in October, commanded the stage in a relaxed manner. He's dropped some of the spotlight basking and "Is all this for me?" hijinks that popped up during previous visits, and that may be why the show clocked in at around 90 minutes.

It's hard to quibble with the effort the Heartbreakers put forth on Saturday night, but the dinner conversation was so pleasant -- and the band's catalog so vast -- that many were left wishing it had lasted a little longer.

ZZ Top opened the show, taking the stage promptly at 7:30 and launching into "Under Pressure."

The Texas trio, celebrating its 40th year in business, may just be the quintessential opening act for an outdoor festival. Drive-By Truckers and My Morning Jacket, who also are doing Petty dates this summer, may be more current but it's doubtful that they'll fill the outdoor sheds from the first note like Billy Gibbons, Dusty Hill and Frank Beard.

"This is one of the good, great nights of American rock right here," Gibbons proclaimed during the set.

Backed by snippets of Westerns and their own iconic videos, ZZ Top choogled its way through hits like "Cheap Sunglass," "Gimme All Your Lovin'," and "Sharp Dressed Man."

In addition to the ultra-tight playing, Gibbons and Hill -- dressed in black -- drove the crowd crazy with a wink-and-a-smirk approach that included tandem shuffling, a Jack Daniels bottle stunt and a fair amount of beard-stroking for the video cameras. After a blistering cover of Jimi Hendrix's "Foxy Lady," Gibbons pulled a young girl -- probably about six or seven years old -- out of the front row to help him play a solo.

The furry guitars came out on cue for "Legs" and Gibbons was back on his black Gretsch for the closers, "La Grange" and "Tush."