The reality TV show Just the Two of Us took liberties with the duet, Curtis Stigers and Penny Smith packing all the finesse of Arthur Mullard and Hilda Baker covering "You're the One That I Want" in 1978. The cringe factor can make such antics a hoot, of course, but true aficionados of the form will naturally look elsewhere.
Many of them have alighted on the career of country great Emmylou Harris, not least because she has duetted with the likes of Bob Dylan, Roy Orbison and Willie Nelson. Country-rock lore being what it is, however, Harris's singing with the doomed troubadour Gram Parsons has generated more column-inches. "Gram taught me how to sing; he gave me a reason to sing," Harris has said of the songwriter and one-time member of The Byrds who out-partied Keith Richards. Her love affair with Parsons was never consummated, but when they covered "Love Hurts" together, the chemistry was quite something.
That was an age ago, and now Harris, aged 60, and ex-Dire Straits linchpin Mark Knopfler are releasing All the Road Running, a gorgeous, thoughtful, many-faceted duets album that was seven years in the making. Knopfler, 56, seems aware that his duetting with someone's of Harris's ilk might raise eyebrows among those familiar with his parlando vocals.
"Don't forget I've risked the theatre of humiliation before," he says, his craggy features settling into a smile. "I've got in there with Van Morrison and George Jones and lived to tell the tale. I'm not posing as a great singer or anything, but I think I've been steadily improving since I gave up cigarettes. Around 1996, I was down to a gasp and a whisper. I thought I'd better drag myself away from the edge of the grave."
Knopfler and Harris first met on a Chet Atkins TV special in 1987; today they are holding court in a huge suite in London's Chelsea Harbour. Knopfler (warm, self-deprecating, dressed in black, as best flatters older rock stars) calls Harris "Em", and gently teases her as one might tease a sister. Harris (perfect nose, string of pearls, dignified in her grey-haired beauty) takes it all in good part.
"When you combine two unique voices," she explains, "it creates a third, phantom voice. Some of those phantoms are more pleasant than others, but I love the third voice that Mark and I create. We noticed right away that our voices blended pretty effortlessly."
Sporadic it may have been, but the recording of All the Road Running was similarly carefree. Two of its tracks - the playful, Cajun-sounding courting song "Red Staggerwing" and the acoustic ballad "Donkey Town" - were originally slated for Knopfler's 2000 solo album Sailing to Philadelphia. "But then I started hearing voices, if you'll excuse the expression, and Em put her vocals on them one Thanksgiving evening in Nashville and they sounded great."
Further sessions were undertaken in 2002 and 2004, the pair now cutting songs from the ground up with the cream of Nashville's session players. But then came more solo albums (Harris's Stumble Into Grace in 2003, Knopfler's Shangri-La in 2004), and the attendant tours and promotional activities put the release of their duets album on hold.
"The crazy thing is that, if you add up the actual recording time, it was less than two weeks," says Harris. "But Mark was so busy that I got the tracks he mixed two at a time over a period of years. It was frustrating, because I had rough mixes of all these great songs, and he'd be like: 'Don't play them to a soul until they're finished!' I was a good girl scout, though."
Listening to All the Road Running, I'd wondered if the opener, "Beachcombing", a song about loss, peppered with Knopfler's expressive, finger-style lead guitar, had been inspired by Hurricane Katrina or the December 2004 tsunami. The line in its lyric that runs: "They say there's wreckage washing up all along the coast..." seemed an obvious clue, but Knopfler says he wrote the song long before the tragedies. The guitar virtuoso can be a hesitant interviewee, his careful choosing of words perhaps a throwback to his previous career as a journalist and a desire to give good quote. While he ruminates, Harris often takes over, her manner supportive rather than domineering.
"There is something prescient about that song," she says. "But I think of "Beachcombing" as a portal to all the other stories on the record. The point is that this world is a dangerous enough place without us screwing around with it. I was telling Mark that I saw a bumper sticker in Nashville that said: 'We all live downstream.' It was a succinct way of saying that everything that happens is going to affect everyone eventually."
Conversation turns to another event whose effect on the world stage has been considerable, namely 9/11. Much of All the Road Running was written in the aftermath of the twin towers tragedy, so it is unsurprising that several of its songs reflect upon its ramifications. Knopfler talks of reading pieces by Martin Amis and Ian McEwan, both of which he found affecting. "I remember the McEwan piece homing in on people in the twin towers using their mobiles; that final phone call home to say: 'I love you.' If there's anything positive to take from 9/11, that expression of love is surely it. That, rather than what happened next: another wave of violence.
"The song 'If This Is Goodbye' definitely came out of that. If 9/11 hadn't happened, I probably wouldn't have written 'This Is Us' either. That's a song looking at two ordinary people's lives, the Polaroid pictures and the drawings by their kids on the fridge. There are bruised people on this record, and Em has a way of inhabiting those characters and making them real."
It is clear that Knopfler's and Harris's family lives are now more important to them than ever. Quizzed about a 2003 motorbike smash in which a collision with a car cost him nine broken bones, Knopfler says the most testing thing was sitting up straight and not laughing at his kid's jokes. Harris, meanwhile, talks fondly of her daughters, Hallie and Meghann, and of the seven dogs and five cats that make her Nashville home something of a menagerie.
What got to Knopfler about the Martin Amis piece, he says, was the writer's realisation that we can't protect our children. "That was something for me to look at," says the guitarist. "I think we addressed it in Em's song 'Love and Happiness', and because you have a man and a woman singing it, both of whom are parents, it intensifies things."
Asked about the song she penned with the Austin, Texas, songwriter Kimmie Rhodes, Harris says that "Love and Happiness" might be the only "proper" country song she's ever written. "You can't get fancy with that genre," she says. "Kimmie and I sat down as mothers and thought: 'What are the things that we would want for our children? What are the metaphors for that deep desire that your child will dodge certain bullets? And what will they need to help them deal with the bullets they aren't able to dodge? Kimmie had the first verse in the bag, and with that wonderful structure of hers, we wrote the rest in an afternoon. Sometimes they come easy."
'All the Road Running' is out on Mercury on 25 AprilReuse content