Prior to the Blues Traveler show, Summerfest had a mellow, "Sunday night" feel to it with a modest-sized crowd enjoying the breezy, beautiful summer evening. Hence, it was surprising how many people piled onto the bleachers at 10 p.m. to witness a show that sparked up Saturday night energy.

At the height of their success in the '90s, the Southern rock / blues band mastered dichotomy, and they continue to do so in 2009. On the one hand, the New Jersey-grown group attracts jam band enthusiasts fascinated by their improvisational live shows, but mainstreamers hooked on decade-old radio hits like "Run-Around" and "But Anyway" are loyal fans, too.

Originally, lead man John Popper's extraordinary size and incredible harmonica-playing abilities added a circus-attraction element to the band's mystique, and the group successfully entertained a variety of demographics for a half-decade before health issues pocked their success. In 1999, bassist Bobby Sheehan died of an accidental drug overdose and Popper struggled with obesity which led to diabetes and emergency heart surgery. Later, he underwent gastric bypass surgery and lost an extreme amount of weight.

Tonight, on Summerfest's Briggs and Stratton stage, Popper appeared large but not obese, wearing his signature black-rimmed hat and a loose-fitting shirt.

Along with four bandmates, Popper ripped through a dozen songs without conversation other than the occasional, sincere "thank you" and a declaration that the show was a tribute to Michael Jackson. (Twice, Popper acknowledged Milwaukee by calling it "Mille-wah-que," referencing Alice Cooper's pronunciation in "Wayne's World.")

But what lacked in words was made up for with sound. The hour-and-a-half performance was almost a single jam -- one song rolled right into the next -- with crowd pleasers like "But Anyway" and "Run Around" mixed in with cuts like opening tune "Forever Owed," the high-energy "Save His Soul," "Look Around," "Freedom," "Hook" and "You, Me and Everything."

Midway thought the show, the band covered Cheap Trick's "I Want You To Want Me," a fitting choice to play in Milwaukee considering Cheap Trick's Midwestern roots, but also slightly melancholy because Popper has lived most of his adult life alone.

Blues Traveler's success started with college radio in 1990 when they released a self-titled CD featuring the song "But Anyway." Their mainstream success, however, was nabbed in 1997 via the album "Four," which included the massive hit "Run Around." Unable to make another chart topper, Blues Traveler was released by A&M Records, but they continue to record with smaller labels.

During Sunday night's show, Popper's voice and harmonica playing were as powerful as they were during the Flannel Era, somewhat surprising considering he's a smoker who indulges in on-stage cigarettes.

Popper's audience appreciation was evident when he threw multiple harmonicas into the crowd after playing them, and his generosity was reciprocated when a concert-goer tossed a bra on stage that landed comically on a microphone.

Although truly the star of the band, Popper respectfully stepped back numerous times to showcase the talents of his band mates, all of whom appeared to be having a great time on stage. But despite his recognition of the other musicians -- and the opening bands -- Popper seems to be an island in the Blues Traveler sea.

Perhaps his solitary way has to do with lingering health issues or his high-profile runs-ins with the law which included an arrest for marijuana possession and the transportation of unlicensed weapons. Regardless, Popper delivered a heartfelt performance and closed the first weekend of Summerfest with a red hot Blues Traveler show.