In a hotel suite overlooking Kensington Gardens, Robert Plant and Alison Krauss are in upbeat mood – as well they might be, given the almost unanimous critical acclaim accorded their Raising Sand collaboration, and its commercial success.
It has secured Plant his highest chart placing since his Led Zeppelin days, entering the US album chart at No2. This is, meanwhile, an unprecedented position for Krauss, whose recordings with her bluegrass band Union Station rely on the core country audience for their gold and platinum discs.
It's a curious alliance, Plant being well-known for his interests in rock, blues, psychedelia, folk-rock and North African music, but never previously exhibiting much of a fascination with country and bluegrass. How on Earth did they meet?
"I saw her picture in the back of Village Voice and phoned up..." deadpans Plant.
"This isn't gonna be good!" interjects Krauss, smiling indulgently from inside a colourful wrap. "Well, I did read the Village Voice on the plane, and there are some provocative pictures in the back, with those 800 numbers..."
"Is it? I must be bluffing!"
The real origin of their current alliance, it transpires, goes back seven or eight years, to when a mutual friend recommended Plant check out the virtuoso fiddler with a view to a potential collaboration. The friend suggested that they duet on a Nashville radio show called Crossroads, which specialises in unusual musical cross-pollinations, but Plant felt he would need to know Krauss better if he was to be comfortable enough to perform live with her. That opportunity came a few years later, when he was invited to contribute to a Rock'*'Roll Hall of Fame tribute to Leadbelly, one of his early heroes.
"I thought, how can I take what I've known about Leadbelly since I was 14, and make it relevant and interesting, without just going and playing 'Gallows Pole'? So I contacted Alison and said, 'What about it?'."
They met for the first time in a community hall in the Armenian quarter of Cleveland, where Plant had already begun rehearsing for the event with Boston band The Tarbox Ramblers. "We're clustered on this little stage when Alison walks in with her fiddle, and immediately I could feel I didn't have to deal with any edge or attitude," he explains. "We instantly got rid of any nervousness there might have been, by bringing out the side of ourselves that might have been the most derisible. She said, 'What key are you singing in?' I said, 'I don't know – normally it's E.'"
"He said: 'Is there another key besides E?'" recalls Krauss. "I loved that."
"Now I know there's B flat, and B sharp," Plant marvels, running with the gag. "And people use capos – there's all sorts of stuff going on."
They sang "In The Pines" together, and despite Plant's inexperience with harmonies, were pleased with the results. "I knew that I was making mistakes," he says, "and that Alison was following me as best she could, without giving me the eyeballs that she does now that we're friends."
"I remember thinking, if we sing it the same way twice, I might be able to catch it," chuckles Krauss.
"Nobody had ever asked me to sing something the same way twice before," protests Plant. "That's the big challenge we're going to have to face when we go out on the road. Half a bottle of Chablis, and it'll be anybody's game!"
Plant is one of the few survivors of rock's golden age who has managed to sustain a restless interest in a wide range of music. And one certainly wouldn't expect a cornerstone of country music – traditionally the most conservative of genres – to have that kind of eclectic spirit, but Krauss, it turns out, isn't your run-of-the-mill country star.
"My parents introduced me and my brother to every kind of music," she explains. "We had Little Stevie Wonder records, Peter Paul and Mary, Flatt and Scruggs; and we went to every concert in the park.
"I grew up in Champaign, Illinois, a college town where there was a great music school, so I heard everything. My mother would take me to rehearsals at the Performing Arts Centre, of everything from kabuki to opera, and symphonies to chamber music, dance performances, everything. So I had a wide range of interests, and an open mind.
"That was when I was tiny, three or four years old. Then when I was seven, I got into fiddle music. Another thing my mother had heard about was the County Fair fiddle contest: I had already taken a year or two of lessons by then, and she said, 'Let's look into this', so we got a record by Richard Greene with a tune that I liked, called 'Little Rabbit', which I decided to learn. My mom said, 'I heard that if you can sing it, you can play it.' At that age you believe everything your parents tell you, so I sat down and listened and listened over and over, and learned how to play it.
"It was the same with improvising – I asked how I might take a solo, and she said, 'You play a variation on the melody.' And she sang me a variation on the melody of 'On the Road Again', a harmony part, which she couldn't really explain, because harmony is all about feel."
Harmonies are at the very heart of Plant and Krauss's work on Raising Sand, and presented the pair with their greatest challenges. Plant is a natural belter, celebrated as the inventor of the dynamic, shrieking blues-rock style that came to dominate heavy rock. But there were always a few quieter, more reflective moments on each Zep album, which hinted at the sensitive soul beneath the libidinal swagger. It's this sensitive side of his vocal personality that has been drawn on for the new album, with the added imposition by Krauss of a more disciplined approach.
"I'm under the control of my master," Plant admits. "And it's so good to be in that position – I've been really open and attentive, and learnt these various parts. When I'm recording on my own, I don't do more than four takes of a song. If I can't get it in four takes, I leave it for a few days before trying again, because I want to put everything into each take. But when Alison and I were recording together, in places I had to be so precise, and what I thought was going to be quite frightening became a lesson to me, a bit like a meditation. I know that sounds a bit stupid, but I really had to concentrate; and when it worked, it was like: glory!"
As can be affirmed by anyone who has heard her work with Union Station, or her collaborations with Emmylou Harris and Gillian Welch on the O Brother, Where Art Thou? soundtrack, Krauss is an accomplished harmony singer with an instinctive grasp of the necessary intervals, tones and timbres that help harmonies gel. It's an art-form that, for obvious reasons, has traditionally been dominated by family groups, from The Carter Family and the Stanley Brothers, through to the likes of the Everly Brothers and the Wilsons.
"Before the Wilsons, there were the Everlys, and before them the Louvin Brothers, and the Wilburn Brothers and the Blue Sky Boys – keep going back and you end up in the same place, 'cos the Everlys were listening to the Louvins, and so on," she says.
"One of my favourite groups for this type of singing is the Cox Family: those family harmonies are just so tight, because everybody grew up in the same house, and they pronounce everything the same way, with the same accent. So it's interesting to have a man and a woman from across the globe, with different accents, harmonising; and when we come together, what makes it special is that we're so different."
The results, on Raising Sand, are quite magical, an alliance of voices as gently heartbreaking as that achieved by Gram Parsons and Emmylou Harris on the classic Grievous Angel, though not as overtly countrified in style. Instead, their harmonies hang almost weightlessly within mysterious, ethereal settings comparable to those devised by Daniel Lanois for Dylan's Oh Mercy and Time Out of Mind, in this case built around the misty haze of subtle guitar parts provided by the omni-talented Marc Ribot and the album's producer, T-Bone Burnett.
Burnett's ability to modernise traditional music modes without sacrificing their authenticity has made him the first-choice soundtrack producer for films such as Cold Mountain and the aforementioned O Brother, Where Art Thou?, and his input was crucial to the success of Raising Sand, not least in determining which songs were included.
"If it weren't for T-Bone, we wouldn't be here now," says Plant. "His guidance and other-worldliness is just fantastic."
"He's a real genius," agrees Krauss. "Before we got the list of songs from him, we were wondering, what's he doing over there? Then we'd get this package from him, with all these incredibly detailed reasons why each song would work."
"It was like an Open University thesis on each tune, explaining why it was important as a piece of music," recalls Plant. "I'd never had a producer like that before, one who asks you to think about it in this way. And there was never even one tiny droplet of irony or short temper. T-Bone's guys, who work as a unit, brought all this gear out from LA to Nashville, and they had to drive non-stop, because they daren't park up somewhere in case the truck was stolen – it was loaded with antique valve equipment, compressors, microphones that they'd got from Latvia and renovated, all of which contributed to that sound. We'd be in glass booths at opposite ends of the room, looking at each other and thinking, we don't even have to sing on this, it's a fantastic instrumental! That sound came out of the truck. And the room. And the awareness of how it should sound."
"He wanted to get everything how it would naturally sound, instead of manipulating it later," says Krauss. "If an amp didn't sound exactly right, he'd find another one that did, rather than try and fix it later."
It's no surprise to learn that the album will be available in vinyl format, a medium that should reveal the music's depth and texture in its full glory. Both singers, like most attentive listeners, regret the supplanting of records by CDs, and not just because of the indisputable loss of sound quality.
"There was such a physical connection to those records," says Krauss wistfully.
"And the amount of trouble you'd go to to get your artwork just right," adds Plant fondly, recalling the ridiculous lengths to which Led Zeppelin would go in pursuit of the perfect cover image. "We'd hold up a release for six months until we got the artwork right: 'Oh, that girl's not in the right position on that rock – go back to Ireland and shoot her again!'"
Plant seems reluctant to discuss the forthcoming Led Zeppelin reunion show, save for an assurance that "it's going to be an exciting evening, quite emotional". While for most fans the emotions will be tied up with their memories of the band, what matters most for Plant is paying suitable tribute to the Atlantic Records founder Ahmet Ertegun, a man whose close connection to the roots of R&B and soul made him a valued mentor to the band. Indeed, one wonders what Ertegun would have made of Plant's current foray – especially given that Plant's own additions to T-Bone Burnett's song suggestions entail country makeovers of New Orleans R&B material such as Li'l Millet & His Creoles' "Rich Woman" and Benny Spellman's "Fortune Teller".
"You can tell I'm out of a beat group in 1963, trying to be black, and getting nowhere near it," chuckles Plant. "Now I'm trying to be white!"
'Raising Sand' is out now on Decca Records