There are few live albums better, or more significant, than the Allman Brothers Band's classic 'At Fillmore East.' From its double-LP packaging to the expanded and extensive songs and solos, the 1971 record pretty much defined the way live albums looked and sounded for the next decade and beyond.

And it's an important historical document too, chronicling a band that had two good-but-not-great-selling albums to its name when it shook the famous New York City venue for two nights in March 1971 with four blistering sets filled with rough and raw blues covers and originals cut from the same cloth. Overnight, 'At Fillmore East' made the Allman Brothers -- especially its two leaders, guitarist Duane Allman and his little brother, singer and keyboardist Gregg -- stars.

Three months after the album's release in July 1971, Duane died in a motorcycle accident that forever altered the group's course in history. They'd go on to score a hit single, a No. 1 album, breakups, disillusionment and a legacy as one of the world's premier jam bands. But they'd never top 'At Fillmore East,' which stands, nearly 45 years after its release, as the centerpiece of a long, storied career.

The original album was comprised of seven songs spanning four sides and 76 minutes, pulled from the March 1971 dates. On the six-CD 'The 1971 Fillmore East Recordings,' the running time is stretched to more than six hours, and the set now includes 35 songs, 15 of them previously unreleased. It also now includes the Allmans' return performance in June that year, when the band was picked by the Fillmore's Bill Graham to play at the famous venue's closing show.

In all, five shows are here (the band played four concerts total on March 12-13, two shows each night). Only 'Statesboro Blues' makes an appearance at all of them, but faves like 'In Memory of Elizabeth Reed' and 'Whipping Post' show up four times each. Because of the Allmans' knack for reworking their songs onstage, however, there are enough differences to pull in fans who think they may already know this material.

But do casual listeners need three versions of 'You Don't Love Me'? Not really. Even if Duane spreads out some tasty licks among them (his simultaneously fluid and piercing solos are highlights throughout). But massive box sets like this aren't made for people who don't already own the essential 'At Fillmore East.' 'The 1971 Fillmore East Recordings' is for fans who've worn out copy after copy of the 43-year-old classic and want to explore the additional performances that were left off, including an epic 33-minute version of 'Mountain Jam' that appeared on previous expanded 'Fillmore' releases.

The bulk of the new and previously unreleased recordings come from the first show on the first date. And at times it's easy to hear why these were the ones that remained in the vaults all these years. The group sounds tentative at times, careful not to step over each other as they circle the perfect groove. By the time they got to the second night and the second show (where most of 'At Fillmore East''s classic cuts come from), they were tightly locked into that groove. And how.