A few years ago, I attended a Tom Petty and the Heartbreakers concert -- it may have been at Summerfest, but I've seen dozens of Petty shows because my college roommate is a freakishly devoted fan of the band -- and the band unexpectedly launched into a cover of the 1969 Fleetwood Mac classic "Oh Well."

I remember thinking "Man, this is cool. It's a ballsy version of a great blues rock tune. The band members really seem to be enjoying themselves and they are kicking the crap out of a great song."

After a few minutes and some extended solos / jamming, a couple more thoughts drifted into my head as I watched people around me talk, text and head for the bathrooms / beer stands:

"Is this getting a little self-indulgent? Has Tom been listening to The Dead again? These guys are great players, no doubt, but are they showboating a bit? Are Petty and the boys doing this to rebel against being 'human jukeboxes' for a crowd of people, many young, who came to hear the hits and may not even know any songs released before 'Free Fallin'' dominated FM radio?"

I pondered those things for a couple seconds, but the spirit of the show and the wafting of nearby marijuana prompted me to re-focus on the show. During the encore, the Heartbreakers launched into another '60s chestnut -- "Mystic Eyes." It was a snarling, sinewy reading of the song Van Morrison wrote with his "Gloria" cohorts in the band Them.

As another long jam unfolded, I wondered about the band's motivation and whether or not I was enjoying what was coming out of the amplifiers.

Why am I relating these stories now?

Because I got the exact same feeling while listening to "Mojo," which came out Tuesday and is the Heartbreakers' 12th studio album and first since "The Last DJ" hit stores eight years ago.

At its core, "Mojo" is a swampy, bluesy collection of 15 songs that come across as relaxed without being ragged and extremely well-played without being extremely memorable. Petty can still turn a phrase with the best of them, and there are some decent lyrical turns on the songs, some of which could be mistaken for covers of Lightnin' Hopkins, Muddy Waters or other blues giants whose records shaped Petty's musical view years ago.

Musically, "Mojo" shares some of the vibe that emanated from Petty's 2008 Mudcrutch revival, but that effort seemed a tad more accessible. Although this is a stripped-down CD, reportedly recorded "live" in the studio without overdubs or studio chicanery, it was complex enough to force this listener replay it several times upon first encounter.

What did I come away with?

For starters, the Heartbreakers are still an amazing band, arguably one of the best of all time.

Though the CD conjures a number of influences -- from "Highway 61"-era Dylan to The Yardbirds to The Byrds and on through the Allman Brothers and early British bands like John Mayall, The Animals and Fleetwood Mac -- it carries their stamp because of Mike Campbell's ethereal guitar playing, Benmont Tench's tasteful piano and the muscular rhythms of drummer Steve Ferrone and bassist Ron Blair. (Scott Thurston, the Heartbreakers' indispensable utility player, contributes some pretty solid harp playing, as well.)

Lyrically, Petty can still change speeds from serious takes on social issues to wry, humorous lines (check out "Candy") that bring a smile.

Whether intended or not, this collection of songs comes across like the band's homage to -- or attempt to overtake -- "Exile on Main Street," the classic Rolling Stones record that is enjoying a reissue resurgence this summer. Only a band with nothing to lose -- either a brazenly ambitious group of young zealots or a collection of old masters -- would have the testicular fortitude necessary for such an undertaking.

The Heartbreakers, with their bank accounts and Hall of Fame status secure, deserve credit for trying.

In several interviews, Petty and his bandmates have talked about this being the type of music "that the band plays for itself" during sound checks, rehearsals and in private moments.

While the songs on this collection may not rack up huge sales numbers (what does these days?) and could send youngsters scurrying to the beer stands this summer, they are pushing their own boundaries.

For a bunch of guys with nothing left to prove, they seem determined to show that there is a lot left in the creative tank. These guys may be too old for a midlife crisis (Petty turns 60 in a couple months), but they still can teach the youngsters -- and even some of their contemporaries -- the first rule about making music: Do what feels true and the rest will take care of itself.