Penn entered music in Muscle Shoals, Alabama in 1957 at 16, head stuffed with R'n'B and sounding like Ray Charles. He soon turned from singer to writer and, after a move to Memphis's American Studio in 1966, producer, too.
Oldham, a session organist whose spectral sound underpins Percy Sledge's "When a Man Loves a Woman", soon joined him. Their songs and sound were vital to what became known as Country Soul. They sank into black music and affected its course.
Strange to relate then that Penn and Oldham were young white boys, raised in segregated neighbourhoods in the informal apartheid of post-war Alabama. "When I met the singer Arthur Alexander in the studio," Penn says, "he was the first black person, other than the person I bought barbecues from, that I ever spoke to."
Penn sits in the lounge of a sleepy Richmond hotel, burly and forceful. Oldham, raw-boned with scared eyes, is by his side, the night before an appearance on Later... (touring their old songs in Britain has already produced a live album, Moments from this Theatre.) It was radio that levered these contrasting souls from Alabama to here. Scything through racial boundaries, it became a lifeline to every boy they knew.
Penn remembers: "Pre-teen, everybody in our part of the country was listening to R'n'B. Then, in '56, here comes Presley and Jerry Lee, and all of that. I wasn't into recording, so when I heard that, it was like it was shot from Mars. It was brand new. We listened to that in the daytime, with R'n'B still going at night. It was a balancing act. With Presley's movies, and Jerry Lee going off on his tangents, with every white singer getting on your nerves, along comes Ray Charles. Day and night. After Ray Charles, I didn't care about white music for a long time. He turned my head around."
Oldham's route to Muscle Shoals was similar. "I got $12 for my first gig, when I was 15," he recalls. "I thought, I haven't had this much money since I picked cotton. So I stayed in bands." He met Penn in a studio in Florence, Alabama in 1965. They wrote together day and night and success was swift. They became a hit factory. When they wrote a No 1 for the future Big Star singer Alex Chilton's Box Tops, a second chart-topper was demanded - and delivered.
"I was tuned into Top 40 radio, and I was tuned into R'n'B radio," says Penn. "I had 'em both in my sights, just like a kid sitting there with a gun. And I would try to think, wherever they are, go somewhere else. That's always been my philosophy for producing or songwriting, because it just ain't much fun running with a bunch. You get trampled."
Like other Southern musicians of his generation Penn has had to wrestle with the mixture of godly and godless in R'n'B, with its Gospel roots. He was "saved" in 1981 after extreme behaviour in the wake of his hit- making almost dragged him under. "I was 'saved' as a child," he says. "But I went as far as I could, and I just about died, before I found a way back to the church house. In 1969, I'd gone out on my own, left American, and built my own studio. I figured I had it made. I had a lot to learn.
"In the Seventies, there were a lot of parties, but not a lot of songs. Whole lot of first lines, and no verses. I lost my studio - stayed pretty intoxicated for eight years. I learnt, though... things that still keep me alive."
Even before this collapse, the glory days for Penn and Oldham were almost done. It was Martin Luther King's 1968 assassination, and the black riots and militancy it sparked, which laid them low. The unlikely bond between races that had forged Southern Soul bent and broke. "It was nothing you could write down, or see in a paper," Oldham says sadly. "It was just in the air. I was the last one to understand it. I wondered why it was, because I'm the same. I play the same, I think the same.
"What had really changed for us was that there were no longer black artists standing in white studios," adds Penn. "It seemed as if a year went by, without anybody hardly being there, of any race.
"It changed my life," he continues. "Suddenly, whatever it was that we had with the black people was gone. I mean, we were basically, if you want to take off the clothes, hillbillies, country boys, cutting black records. That's what made it sound like it did. We didn't do it as good as Detroit, as good as Stax, but what came out of it is what they call Country Soul... so it changed all of our lives, Martin Luther King's death."
But do they feel equipped to write for the world as it's become? "I'm always trying to write pop music," says Penn. "It would be nice to have a young person who was doing well that we could write for. Not just for the money, but to help them. I feel we probably know how to write songs."
'Moments from this Theatre' (Proper Records) is out now. Dan Penn and Spooner Oldham appear on 'Later...' this Saturday on BBC 2
The Dark End of the Street James Carr (1967)
Written by Penn and Chips Moman. A bleak hit, in which unfaithful lovers exist in private hells. The endlessly covered signature tune of Carr, soon lost to demons of his own. "I hear sometimes he has himself together," says Penn. "When he does, he justtears people up... When he can't, he stays indoors."
When a Man Loves a Woman Percy Sledge (1966)
Oldham's most famous studio moment. His churchy organ is what makes Sledge soar in this worldwide hit. "He stood there and sang his heart out," says Oldham, "I'd played on hits before, and it struck me that day it was special."
Bob Dylan (1980)
Oldham played thoughtful organ on Dylan's most evangelically religious, unpopular album, and the confrontational tour that accompanied it. "There were people with placards protesting. We'd play, and half the audience would boo. He said to me, "I welcome the controversy - let 'em ask questions, let 'em talk to me."