For a star of his magnitude, once the singer in the biggest band on the planet, frontman of the only group to seriously challenge the Rolling Stones' perennial claim on being the raunchiest of rockers, Robert Plant has managed to retain an admirably down-to-earth attitude to life. Matey and approachable in circumstances to which most stars react with bristling petulance, Plant seems to have mellowed well with age – as too has his music, which, over the years, has developed a burnished grain and texture comparable to that of the folk and blues heroes who originally inspired him to pick up what he calls "the great flaming torch of rock'n'roll" and run with it.
These days, he's more fascinated with the acoustic subtleties of North African scales and North American harmonies than with the bludgeoning power of electric blues-based rock music. Indeed, when Plant went to see his former Led Zeppelin bandmate John Paul Jones's new rock supergroup Them Crooked Vultures at the Royal Albert Hall a few months back, he admits his ears "bled for two days" after the sonic assault. "But I feel so far away from heavy rock now," he reflects. "It's quite odd, how mine and John's paths seem to have crossed over – we've sort of gone into each others' worlds a bit."
It's an intriguing development, and one which could hardly have been foreseen during Plant's tenure with Led Zeppelin, when his falsetto shrieks and erotic double entendres combined with Jimmy Page's steamroller riffs to effectively invent the heavy rock grammar. Founded in the late 1960s, initially as The New Yardbirds – an attempt to glean some publicity from Jimmy Page's status as the last of The Yardbirds' stellar guitarists – Led Zeppelin were an alliance of extraordinary talents. Bass-player John Paul Jones, like Page, was a veteran session musician whose facility with keyboards and as an arranger would help furnish some of the textural depth that set Zeppelin apart from their peers. John Bonham, a friend of Plant's from the Midlands heartland of heavy rock, was perhaps rock's greatest powerhouse drummer, eschewing the fussy jazz filigree of such as Cream's Ginger Baker and Jimi Hendrix Experience's Mitch Mitchell in favour of a crunching, dynamic rhythmic undercarriage that was strong enough to carry the heaviest of riffs.
Jimmy Page himself was a dazzling technician with a questing, experimental spirit: even at the band's earliest shows, he was playing guitar with a bow, and incorporating a small Theremin to broaden the sonic palette with outlandish electronic effects. I vividly recall seeing the band in its infancy at Nottingham's Boat Club, where, despite packing as many decibels as groups like Earth (later Black Sabbath) and Free, the massive riff-driven songs boasted a superior finesse and subtlety which has rarely been equalled by later generations of heavy rockers.
But it was Robert Plant who was the decisive onstage presence, the quintessential rock'n'roll combination of sylph-like grace, crushed-velvet style and banshee blues-wail falsetto, capped with the waterfall of blond ringlets which, even as he turns 62, still form a resplendent cascade down his back. Although his countenance is more gnarled than in his youth, he yet commands the kind of rough-hewn appeal that doubtless still charms the pants off ladies half his age. Since his marriage ended in 1983, Plant has settled into a comfortable lifestyle as a rural rock squire, whose girlfriends have included the singers Najma Akhtar, Alannah Myles, and Tori Amos, his most substantial recent relationship being with Jessica Jupp. He had three children with his wife Maureen: Carmen Jane, Logan Romero and Karac Pendragon (who, sadly, died aged five in 1977); and another son, Jesse Lee.
Plant's distinctive mane of hair, in certain situations, continues to exert a strange fascination. "When I played in Essakane [in Mali, home of the Festival in the Desert] about five years ago," he recalls, "we were rehearsing 'Whole Lotta Love' in this tent, and it filled up with locals who, I later found out, were mainly discussing whether I was a woman. I thought it was because of my singing, but no, they just wanted to know if I was a chick!"
But at least their reaction was more restrained than that of the local women who were hired for a North African video shoot to promote one of Plant's 1980s solo releases.
"I got chased around the sand dunes by a bunch of women we'd hired to come over the dunes doing that Berber dance thing," he chuckles. "I'm singing this bollocks, 'what kind of fool am I...', and whenever we went out of sight of the cameras, they were just chasing me, trying to get hold of my old chap, to have a look! If there'd been a good-looking one, I could have done a deal, but as it was, I kept shouting, 'for god's sake, roll the camera!', and when I came over the top of the dune, I was flushed from running. They just didn't give a toss, 'cos they were either widows or prostitutes, so they had no social status. And they were miles away from their villages, so they were just running wild."
The story makes for an ironic comparison with the singer's time in Led Zeppelin, when the band became notorious for the carnal excesses to which they subjected groupies.
Led Zeppelin still exert a powerful grip on many rock fans, as witnessed by the response to the group's 2007 comeback performance at the O2 arena in tribute to Atlantic Records' late founder Ahmet Ertegun. But not, oddly enough, for Plant himself, the only original member of the band less than enamoured with the prospect of a longer-term reunion, turning down a reputed $200m offer to re-form the band on a longer-term basis. But then, by the time that show was being planned, the alternative career which he had spent over two decades developing was bearing spectacular fruit with the Raising Sand album recorded with bluegrass singer Alison Krauss. Released a couple of months before the Zep reunion show, it went on to scoop a shedload of Grammy Awards, including Album of the Year.
Raising Sand effectively condensed into more potent form Plant's growing fascination with folk and country music, which is extended on his forthcoming follow-up album, Band of Joy (named after his Sixties group). This features a diverse selection of material ranging from antique blues and folk pieces such as "Satan, Your Kingdom Must Come Down" and "Cindy, I'll Marry You One Day", to songs written by Townes Van Zandt, Los Lobos, Richard Thompson and indie trio Low, made over in a variety of American roots styles.
Jangly folk guitars, banjos and mandolins collude with the deep, throbbing Native American pow-wow rhythms, skirling electric guitar drones, glistening pedal steel, chain-gang gravel-shaker percussion, Fifties rockabilly twang and vocal harmonies which draw on both gospel and Appalachian mountain music. Not once does Plant attempt the sky-splitting, larynx-shredding screams for which he was once renowned; instead, the more reflective, homely warmth of Raising Sand is employed to throw new light on further hidden corners of American musical heritage.
"For me, it's no longer to do with vanity, ego, and visible success," says Plant. "It's just about getting down into the earth of music. I spent three, four, five years never playing a Zeppelin song, from 1981 onwards, because I didn't just want to lean on Zeppelin. I've gone from being in that huge band to picking up the pieces of my own gift."
His friendship with Alison Krauss seems to have reignited in Plant a long-dormant affinity for the simple pleasures of family music. "She loves to sit around in the parlour singing those old songs with whichever family's coming into town," he explains, "in the same way that my grandfather used to do in the Black Country: they'd sit around with fiddles and sing. I never thought it had much relevance, until I realised that all of my memories of my father's father were jubilant. He was very funny, and he was the founder member of a famous Black Country brass band, he played piano, trombone and fiddle. My dad played fiddle as well. Three Roberts, we were."
Somewhere along the way, however, that family connection became strained in a way which was not the case, he realised, with the American musicians in the Raising Sand band, especially guitarist/singer Buddy Miller, who serves as musical director of Band of Joy.
"When I was a kid, I was following black soul music," he explains. "Deep soul, from the American South, what in the end was bastardised into Northern Soul. I remember taking the money from my Saturday jobs and sending off for an import copy of James Brown Live at the Apollo, on King Records, very heavy vinyl.
"But if you go through all the little black soul labels around the various cities – Philadelphia, LA, Houston, wherever – the Memphis records had a real edge [this was before Stax]. And as well as his Nashville country references, Buddy had all these rhythm'n'blues points of reference as a guitarist and songwriter which we weren't privy to over here in the UK – we only got the hits over here, on labels like Stateside and London American.
"These people that I meet have got way more depth than I have – I mean, I know lots of stuff, but it's quite fluffy in certain areas! But they've just got it, they lived with it all the way through, from the radio, from their uncles and aunts, whereas my parents' approach to the music of my adolescence was one of horror, because of what it represented. Yet my father was the same age as John Lee Hooker, who was in Detroit singing 'Boogie Chillen' the year I was born! In America, whether it be Woody Guthrie, Fats Domino, the early Elvis, all those guys up in the mountains, music was coming out of the churches and from around the fireplaces, off the steam radio, onto the street, and it gambolled out."
This notion – of what's known as a "big sing" – is central to Plant's current endeavours, which is why Patty Griffin has been drafted in to provide harmonies alongside Buddy Miller, who previously sang sweet back-up on many Emmylou Harris records. After years of being the lone frontman, the idea of sharing the vocal spotlight with others is something Plant finds very refreshing.
"There are always generic terms like 'Americana'," he acknowledges, "but there are no boundaries as to where it can go." Not that boundaries have figured that highly in Plant's career anyway. Even during the Led Zeppelin years, the group's core blues-rock riffs were frequently augmented with folk music and the kind of North African influences (as on the mighty "Kashmir") which would provide inspiration for parts of Plant's solo career. He first encountered this beguiling Arabic strain on his first visit to Marrakesh in 1970, when he was "driven to distraction" by the Egyptian singer Oum Kalsoum.
"I was intrigued by the scales, initially, and obviously the vocal work," he says. "The way she sang, the way she could hold a note, you could feel the tension, you could tell that everybody, the whole orchestra, would hold a note until she wanted to change. When I first heard the way she would dance down through the scale to land on a beautiful note that I couldn't even imagine singing, it was huge: somebody had blown a hole in the wall of my understanding of vocals. There was just no window for it here, literally nothing at all in 1970 that said, 'this is the music of these people called Berbers, they move around the Sahara, they speak the same language despite being separated by vast distances, they have their own culture, they were the people who inhabited North Africa before the Arab invaders, and they are a uniquely spectacular people, both in terms of song and appearance and culture'."
For all that, the more Plant investigated this (then) alien music, the more correspondences he found with Western music.
"If you play North African chord progressions, quite often you'll find that it's similar to the way that Pentangle, or whomever, played," he explains. "There's a similarity between European and North African folk musics. The early Cheb Khaled stuff, I used to buy the cassettes in Morocco, and go home and work out the chord progressions, and it was 'Matty Groves'! Everybody's going round the same things."
Likewise, Plant finds many correspondences and links between traditional British folk music and the country music of the American south.
"Once I'd found these old bits of creaking music echoing down from the hills, there's so much of what I'd always wanted there to be in Britain there, which is very hard to find in these islands now," he reflects. "I think a lot of the stuff that I experienced in Tennessee and around there is basically music of the 18th and 19th centuries from these islands which came over with British and Irish settlers; but it's alive and well, and not being reduced to some kind of glorious middle-aged celebration of pissing it all up the wall. We are a little island, and because the music entertainment structure is so minimal, you aren't allowed to encourage fringe work to become mainstream. There should be a healthy scene that runs alongside cabaret for people of a certain age, so it doesn't have to be Lulu or David Essex, the Tin Pan Alley stuff. That's my current infection – that with the right apparatus, I can continue this adventure in finding out: it's not even looking for obscurities, it's looking for something that's tangible."
Then again, even the tangible traces of history and heritage are always dependent on where you're coming from, and which way you're heading, as Plant discovered when he was in Mississippi recently to sponsor a blues-heritage plaque in association with the University of Mississippi Historical Society.
"There's a general store in Friars Point, Mississippi, run by a Jewish family, and it's where Robert Johnson used to play outside of when he was in town," he says. "I went in there and bought some snacks, it was a pretty beat-up old place, in a not particularly affluent area, and I said to the old guy in there, 'how do you deal with the fact that, for many Europeans, this is a place connected with a blues legend?'
"'Oh, don't talk to me about Robert Johnson!' he said. 'My father used to moan and moan in his old age over how much business we had lost because Robert Johnson always chose to sing under our awning.' There'd be a huge crowd gathered around to watch him play, and customers couldn't get to the store! You don't get that in Rochdale, much as you'd like to. It's not part of the natural flow of these islands."
'Band of Joy' is released on 13 September