Blues Traveler is managed by David Graham, son of rock promoter Bill Graham, The elder Graham, who died in a weekend helicopter crash, was buried Monday after a West Coast funeral attended by his son and close family. Meanwhile, Blues Traveler stayed out on tour, per Bill Graham's wish. "He always said that if he went, no matter how awkward the circumstances, that we should keep on playing." tour manager Dave Precheur said Tuesday night. "He was always great to us. He got us on a number of bills with bigger bands, and some large festivals. He got us on a homeless benefit before a quarter-of-a-million people in Washington two years ago with Jefferson Airplane and Los Lobos. Even though our name wasn't worth a dollar at the time, he cared." Blues Traveler, a hard-blues groove band from New York, avoided any somberness Tuesday night. They stoked some levitating jam session grooves snapped up eagerly by 1,800 dancing fans, including many Deadheads. Only a year ago, the little-known Traveler played a discount show at Nightstage (anyone in a tye-dyed T-shirt got in under price), but this year they're Orpheum headliners. They've made the jump thanks to the incomparable word-of-mouth among Deadheads: and to recent airplay on WBCN from the aptly titled tune, "All in the Groove." If you like a rowdy jam session, then Tuesday night was your ticket. Instrumentally, the four-piece Blues Traveler were impressive, especially funk-metal-edged guitarist Chan Kinchla and harmonica whiz John Popper, who merged the traditionalism of Paul Butterfield with the jazz flights of Sugar Blue. The two-hour, solo-filled set churned up your juices, though at times the songs felt one-dimensional, as the grooves overwhelmed any grace. Vocals were also a weak link, as Popper seemed more comfortable blowing harp than singing lyrics. One backstage excuse was he was using an old mike. Another was that the sound engineer was having problems. Thankfully, the adrenalin rush from the jams was enough to compensate. Opener Widespread Panic were a widespread delight. An Athens, GA, band signed to the revived Capricorn Records (the Allman Brothers' old label), they were highly impressive. They, too, had a retro sound, mixing Allmans grooves with singer John Bell's guttural, lizard-king vocals a la the Doors' Jim Morrison. But their songs were more varied than Traveler's, moving from slipbeat, Grateful Dead-like shuffles to a seductive blues cover of Robert Johnson's "Me and the Devil Blues," with guitarist Mike Houser and keyboardist T. Lavitz (formerly with the Dixie Dregs) weaving dual magic. Instead of an intermission between sets, they were slowly joined by Traveler for a tumultuous jam before leaving. The two groups joined again later for a fitting climax on Van Morrison's "Gloria."