But that's only the beginning: Between the head-scratching cover versions and jaw-dropping live cuts, the off-the-cuff interview snippets and the onstage sermonizing, Anthology works as an audio biography and actually makes sense of one of the most mercurial performers in pop history.

Born in Arkansas and raised in Michigan, the twentysomething Al Green was pretty green when he met the Memphis-based producer and bandleader Willie Mitchell, in 1969. With his background in gospel singing and a small R&B hit ("Back Up Train") under his belt, Green was itching to find a place in the commercial soul-music boom, and Mitchell and his Hi Records house band turned out to be ideal collaborators. Grunting his way through a decelerated version of the Temptations' "I Can't Get Next to You" and his own feisty "I'm a Ram," Green proves here that he could have been a funk contender. Rather than repeat the late Otis Redding's winning formula, however, Green and Mitchell took their artistry to an even higher plane.

"Tired of Being Alone" made its mark in 1971, crossing over to the pop charts and establishing a signature sound along the way. Buoyed by the fat bass-and-drum bottom and an ethereal, floating melody, Green cajoles an estranged lover and carries on a soul-searching conversation with himself. Overwhelming emotion is held in check by sheer willpower – that bare-knuckled control became Al Green's calling card.

From there, the floodgates opened: During the next few years, "Let's Stay Together," "I'm Still in Love With You," "You Ought to Be With Me," "Call Me (Come Back Home)" and "Here I Am (Come and Take Me)" fed an apparently romance-starved public. Co-written by Green with Mitchell and various band members, these songs are still vibrant and irresistible today. Supported by the subtle grit and fire of the band, Green was free to pursue his muse. Economy is a watchword for the Hisound, not only in the tart horn arrangements and jazzy chord progressions but in the recording itself. The primitive conditions under which the band toiled resulted in one-take efficiency and on-the-money musicianship.

A different kind of tension emerges in Green's mid-'70s work. The conflict between blues and spiritual influences became even more crucial once he was "born again," in 1974. "Jesus Is Waiting," off the classic Call Me album, can now be heard as the pivotal step in Gr