“Welcome, my friends, to the show that never ends.”

Emerson, Lake and Palmer may have sung that first, but Blues Traveler could easily adopt that as their motto today.

They dazzled a large crowd of fans Thurday night at Alfond Arena with a show that lasted two hours, which was filled largely with long-running examples of their musical virtuosity.

Their set got off to a late start. It followed an interminable intermission, during which the public-address system blasted most of the dance hits of the ’70s, as students danced to songs that their parents had grooved to before they crossed over to adult contemporary.

A pattern was set early in the evening. Lead singer John Popper would bleat, scat or rap a verse, and maybe a chorus, then he’d whip out his harmonica, and he, guitarist Chan Kinchla, bassist Bob Sheehan and drummer Brendan Hill would take off on an extended jam. Repeat the process three times, and most songs would stretch out to anywhere from five to 15 minutes in length (The exception was the power ballad “Yours,” a welcome change of pace).

The young audience didn’t mind this approach a bit, dancing along feverishly. That glazed look on many faces didn’t come from substance use; rather it was exhaustion from dancing. Many forgot the event was a marathon, not a sprint.

Blues Traveler mostly skipped hits such as “Run-around” in favor of lesser-known album cuts and songs off their current album “Straight on Till Morning.”

Popper, wearing his trademark black hat and a bandolier filled with harmonicas, showed why he is considered probably the top rock harmonica player. Kinchla took his turns soloing as well, head thrashing as he assaulted his guitar. Hill aggressively attacked his drum kit. Sheehan stoically plucked at his bass while chain-smoking cigarettes. (At the same time, security and fire personnel furiously and futilely sought to quash smoking on the tarp-lined arena floor. Oh, those double standards.)

Still the end came suddenly. After Popper said good night, the foursome was coaxed back for an encore. Someone in the audience gave the singer a “Popper for Council” sign, and he did an impromptu stump speech. Then they did a quick one-song encore, threw harmonicas to the crowd and left for the night. Even after all that, they still left some wanting more.

Opening the show was the intriguing Virginia quartet Agents of Good Roots. They, too, favored a jam, but theirs took more of a jazz fusion approach, featuring the sax of J.C. Kuhl and the keyboards and guitar of vocalist Andrew Winn.