"What is hip?" Gov't Mule front man Warren Haynes asks on The Deep End Volume 2, his band's new album. For starters, it's not something anyone who'll stand onstage at the Gypsy Tea Room on Tuesday night knows much about, which is totally why you should go. These guys are unreformed music geeks, and their enthusiasm is as contagious as the head lice that no doubt circulates at the jam-band festivals the band often plays. Even that increasingly open-armed scene (surely the avatar of anti-hipdom if there is one) might scratch their heads at some of the guest players who pay tribute to late Mule bassist Allen Woody on The Deep End discs: Former Metallica man Jason Newsted, Yes' Chris Squire and Me'shell N'degeocello don't seem like Phish fans, do they? Openers the Drive-By Truckers are even less concerned with fitting in: Their latest album is a two-disc Southern rock opera called Southern Rock Opera, they number three guitarists among them and they dedicate the record to Lynyrd Skynyrd, "America's greatest rock and roll band." But as with Haynes' crew, spirit (and slash-and-burn guitar solos) is everything here, and SRO's dense libretto alone is something to marvel at. Plus, they're smart: "When the paramedics got there, they could still hear 'Free Bird' playing on the stereo," front man Patterson Hood sings of the gnarly car accident that opens the story. "You know, it's a very, very long song."