Gov't Mule has such a massive catalog of songs that front man Warren Haynes says it's unlikely the band will repeat any of them during its two-night run at the Tower Theater. In fact, he says, it's possible that none of the songs played in Philly will even make their way to New York's Beacon Theatre for the quartet's two-night stand there.

"It's literally hundreds of songs," the soft-spoken guitarist and singer said. "We usually go for three hours or so. It ends up being a long night, but you're pleasantly exhausted at the end of it."

Based on the fact that Haynes is a full-time member of both Gov't Mule and the Allman Brothers Band - and has a solo career - you'd expect him to be, uh, pleasantly exhausted offstage, too. But the musician, 52, whose controlled intensity nabbed him the No. 23 spot on Rolling Stone's "100 Greatest Guitarists" list, says he is quite energized by his musical path.

"It's not work if you enjoy what you're doing," said the North Carolina native and New York resident. "Sometimes, the traveling and staying in hotels and eating bad food can be tough, but the music itself always feels great."

Gov't Mule was formed in 1994 as an Allman Brothers side project by Haynes and the bassist Allen Woody. It almost closed up shop after Woody's sudden death in 2000. But Haynes now says he expects it to outlive any other project he's involved in.

"Gov't Mule is the perfect laboratory for us to do whatever we want," he said. "Each record is different than the one before. And the great chemistry between us, as musicians, is something we always come back to."

While generally labeled a "jam band," Haynes said, that's only partially true, as the group "doesn't really sound like any other of the jam bands out there.

"We take a very jazzlike approach to the improvisation, but we're very much a rock-and-roll band," he said. "We play what's in our hearts, and we never second-guess the marketplace or even our own audience. All our influences rise to the surface in the music - and there are a lot of influences."

The band enjoyed its first-ever extended break last year, which Haynes used to record his solo album Man in Motion and tour in support of it, as well as playing gigs with the Allmans and Grateful Dead bassist Phil Lesh. Gov't Mule's forthcoming album, tentatively titled Shout, will be its first studio effort in nearly four years.

"It's the most diverse record we've ever made, influenced by everything we love," Haynes said. "It reflects all our tastes." Fresh off its 24th annual fund-raising Christmas Jam (for Habitat for Humanity), Gov't Mule plans to treat Philly fans to some of its new material.

"We'll get up on that stage and see where things take us," Haynes said. "There should be some surprises."

Gov't Mule plays at 8 p.m. Dec. 28-29

at the Tower Theater, 69th and Ludlow Streets, Upper Darby.

Tickets: $26.25-$55. Information: 800-745-3000, www.livenation.com.