From early hits like "Guilty" to his platinum-plated ’70s, Al Green has represented love both river deep and mountain high. His is a past filled with raw romanticism that could tear at the sacred heart of who Green is now: the Reverend Al of the Full Gospel Tabernacle Church of Memphis.

That schism has divided the best of them. How do the deeply religious sing of the darkly sexual with such dedication?

"From the beat of the blues to the bop of jazz, you’re either writing to God and to Christ or to your lady," says Al Green, who interrupts his declarations of the separation between church and mates to croon blues refrains ("My baaaby done left me."). Long before R. Kelly, Green’s throaty baritone and free-flying falsetto cut into frank, sensual smashes like "Tired of Being Alone," "Call Me" and "Let’s Stay Together."

Recorded by Green’s co-writer and producer, Hi label boss Willie Mitchell, at his Royal Studios in Memphis, these were the height of sexed-up, secular hit-making songcraft. It’s a craft Green left behind in 1979 to become a gospel-only crooner. But how he came to reunite the devil and the divine -- more than any other singer, save, perhaps, Solomon Burke -- and reconvene his legendary partnership with Mitchell is the story behind I Can’t Stop (Blue Note), their first collaboration since 1977. Everything Green writes now is about commitment: to God, to faith, to his wife.

"I do my duty. I’ve given myself over to God. I’ve asked him as to how I could spend my days singing about a gal when I’m thinking about you, Lord," says Green. "But God told me that he gave me those songs and that voice for me to share, to make my living for my wife and my children. 'That is your job, Al. But you’re duty is to me.’"

God wants Al to sing old songs like the riveting, rhythmic "Take Me to the River" and new ones like the teary-eyed ballad "Not Tonight" -- all with the same stuttering horns, tom-riding beats and Hi organ whoops of yore.

"I’m not in control here. I can’t choose to just pick a gospel song or pick a secular song."

To some, Green’s sweet-but-sensual sound represents love beyond passion, a dearness that brings couples to him -- no matter where he is -- with the request that the Rev. Al marry them. "'From Tokyo?’ I ask them," he laughs. "I’ll do it. The music is a part of my house. It’s an honor if it’s so much a part of theirs."

To Green, doing a secular song requires a permission slip. "I have to know from him if it’s the right thing," Green says. "And then my mom has to hear it. She says, 'If you mean what you’re saying Al, really mean it, then that’s nice.’"

The listener becomes privy to what Green says, now, are secrets. Gone are the days of being "a cigarette smoker and a practical joker." Rather, the intimacies shared within I Can’t Stop are the holy passions of Green and his wife. "She thinks I’m giving away our private moments." Instead, Green divulges tales of married love in a blunt, metaphorical style that’s as sexy as any wantonly ribald escapade.

"That’s what Willie wanted," says Green, in a whisper, of recording I Can’t Stop with Mitchell. "Willie said, 'I don’t want to do no gospel. No cover tunes written by somebody else 25 years ago. I want you, Al, to write from the table that is that heart of yours. I want the bread. I want the crumbs.’" Green knew what Mitchell required: everything Green is now. "He wanted what was in my heart and on my mind."

This is how Green came to write secularly now; by asking God, by presenting the proposal to his church. "The pastor said, like my mom, 'Don’t shuck and jive; if you mean it, release it.’

Still, it’s not far off from his once-innovative ways -- ways that, between 1971 and 1977, were unbeatable. Melodically, rhythmically and vocally, the clarity of Green’s music was rivaled only by its gracefulness, grit and intimacy in the face of its sexuality. The same hedonism found in his voice could be found then in his way of life. Famously, Green was a Grammy-winning, gazillion-selling creature of the flesh who loved his wine, women and drugs. Whether you hear Green sauntering through "Let’s Stay Together" or see pictures of his friendly bedroom eyes in his autobiography, you know he was soul’s grooviest smoothie.

"I felt, from my music, the same thing everyone else did. Still do. I’m a man. I ain’t quite dead yet," he laughs. Only now, temptation is part of the music without being part of Green.

"Temptation’s not a bad thing. A thing is only sin when the knowledge and intention is present. If you have the intention -- everything can be sin. I just don’t perform those things," he laughs hard. "I’m a pastor right? But look at Moses and Abraham … with their women up until their old age … mmm-hmmm."

Age hasn’t stopped Green, 57, or Mitchell, 75, from reuniting for I Can’t Stop in the same fashion with the exact sound -- recorded at the same studio with the same RCA mics -- their classics were. Green remembers meeting Mitchell at a concert in 1969. After being eyeballed by the well-known producer, Green wanted to know why the wily Mitchell was grinning. "With that voice, I can make you a star," said Willie. "How long is it going to take?" asked Al.

As soon as they joined forces, Mitchell sought the "Al-within," a laboriously frustrating process that, upon yielding the full fruit of Green’s passions, never stopped blossoming. "One night, Willie hit the machine and out came 'I … I’m so in love with you. …’" You can practically hear Green licking his lips at the memory.

"I can’t imagine how Willie got such a big sound on that little Ampex board," he says. Add in the legendary backbeat of the now-late drummer Al Jackson, trumpeter Mitchell’s ideas on stammering brass and swirling organs, and you have The Sound. It’s a feeling and groove that figured -- with exact precision -- into the process of writing and recording, in 2003, the raunchy "I’ve Been Thinkin’ ’Bout You," the exquisite "Million to One" and the rest of Stop.

Time has forgotten Green. He holy-rolls his voice across Southern-fried funk and Philly soul sweetness as if it was 1973. Yet, nothing sounds re-fried. It’s not retro. Rather, after more than 20 years of not recording together, they sound as if they never missed a beat. "Once you get the whole package, Al and Willie at the piano, putting out, working through blood, sweat and tears, you can’t help but have that sound," says Green.

With that, not only is I Can’t Stop a lovely celebration of the Green-Mitchell collaborations past and present, but of its future -- an acknowledgement of time lost and good grooves to be found throughout a klatch of new sessions that will yield both an R&B hip-hop album and a jazz duet between the friends.

"Know what the old man Mitchell says?" asks Green. "If we’re going, let’s go. If we ain’t, let’s stay home."

Al Green and Cassandra Wilson, Sun., Feb. 15, 8 p.m., $45-$65, Tower Theater, 69th and Ludlow sts., Upper Darby, 215-336-2000.