"The first session I did in New Orleans was with Bobby Charles," he tells me, "and the first record I remember hearing was my brother's 78 of 'See You Later, Alligator', which was written by Bobby Charles." Such pleasing juxtapositions come easily to a musician who played his first paid gig at the age of 14, and recorded widely on both sides of the Atlantic.
Simpson, 52, grew up in Scunthorpe, in a household filled with music. "My father was born in 1899, and he was basically a Victorian gentleman, who sang Gilbert and Sullivan and light opera. He taught me how to enunciate." His mother and brothers filled the house with African-American music - Paul Robeson, rock'n'roll 78s, blues and jazz. "And when I got my first guitar in 1965, the folk revival was at its height. Between the ages of 12 and 17 I could walk round the corner to the Scunthorpe Folk Club and see the cream of musicians working that circuit." That meant the likes of Martin Carthy, Bert Jansch, Nic Jones - influences who have since becoming sparring partners.
In terms of his distinctive technique, the five-string banjo with its altered, modal tunings, was a key development. "It was initially a home-made instrument," he explains, "and very hard to intonate, so they devised tunings that had as many notes of the scale on open strings as possible." He applied these tunings, and the banjo's playing technique, to the guitar. "It's called flailing, where you play with a downward stroke, the very opposite of how you play guitar. I was a kid trying to play the Delta blues, but I didn't have 200lb of muscle to throw at the guitar, so I came up with these banjo scales."
Applying these new tunings to the guitar gave him the weight a teenaged Simpson needed to climb into the circle with heroes such as Blind Willie Johnson and Big Joe Williams. "I became a bit of an impressionist," he says. "Not in terms of being an impersonator, but I could take and represent part of the essence of what they were doing and capture the feeling without trying to sound like them."
He sounded more like himself than anyone else early on, and quickly made a name on the circuit. "I was always being told to make up my mind about what I was going to do, either folk or blues," he says. "And I said, I don't think that's true. It's all the same music, just different angles of the song. The songs started before the music. I felt that these were all avenues I could go down, and I could find more of myself in those directions."
The song-collector Bill Leader released his first record in 1976, and the following year he walked away from a management deal with Tony Secunda, who had plans to make a guitar hero out of him, and embarked instead on a partnership with the great English singer June Tabor. Their collaboration resulted in three classic albums through the Eighties - A Cut Above, Abyssinians and Aqaba - and the partnership was resumed on 2003's An Echo of Hooves. Tabor's new album featuring Simpson, At the Wood's Heart, has just been released.
"I learnt about flexibility," he says. "When you work with a singer as good as June, you don't ask questions about when she's going to do something. She had a total unaccompanied singer's approach. Having my first experience of that kind of thing, I'll never forget it. A guitar player will put things in strict time, and with June you had to learn to do the opposite. If you add just a couple of extra words to a line, it can throw the whole nature of a song, and give it a very different feel. I listened hard, and if she made a mistake, I would too, basically. There's a symbiosis between the two of us."
The songs they choose are suffused with the mystery, magic and mayhem of the British tradition. "The best definition of this kind of music I've ever heard," says Simpson, "came from an 11-year-old in a school workshop, who asked me, why are your songs all about law and order and movement? And that's a beautiful way of describing that certain area of traditional music."
It's a fair summation of much of Kind Letters, whose songs are full of flight and migration, and murder and transgression. Take "The Flying Cloud", an astonishingly vivid narrative of seafaring, slavery, piracy and the gallows, told with all the inexorable force, brio and body count of Jacobean tragedy. "It's exquisite, massive storytelling," says Simpson. "The amount and the quality of texts is mind-boggling." Assimilating the song from different sources, he plays his way into its immensely powerful heart with the flexibility and intuition of a master accompanist, drawing out its essence with superb guitar figures that catch the song like a net.
He is firmly of the belief that the folk tradition is not a museum but a living, evolving, habitat that you keep alive by playing it. "It's a fantastic time for music," he says, remarking on the vitality of the British folk scene he has returned to after 15 years in the US. "Since I've been back, I've worked with June Tabor, toured with Eric Bibb, recorded a BBC4 session with Dick Gaughan, been out with Martin Carthy - and it just doesn't get much better than that."
Martin Simpson plays The Vortex, Gillett Street, London N16 (020-7254 4097) on Monday. 'Kind Letters' is out on TopicReuse content