How does a four-piece rock band set about covering a composition like Yoko Ono’s 1961 Voice Piece for Soprano, a set of notes reading simply – “Scream. 1. Against the wind. 2. Against the wall. 3. Against the sky.”? Presumably, its copyright is infringed by millions of mewling babies or arachnophobic women worldwide on a daily basis. But it takes veteran New York art-rockers Sonic Youth, and Coco, the toddler daughter of band members Kim Gordon and Thurston Moore, just 12 seconds to dispatch it and, against all odds, emerge with their dignity intact.

Sonic Youth’s new album, the archly titled Goodbye 20th Century, is a double set of 13 post-war avant garde pieces by the likes of John Cage, Cornelius Cardew and Steve Reich, but it doesn’t represent as much of a departure for the former rock-festival headliners as the casual listener might expect. “We’ve been doing experimental work all along,” protests guitarist Lee Ranaldo, predictably. “It’s just that now we have our own studio, we’re able to record it in a releasable form. We’ve never been strictly pop or avant garde, we just follow what we like. That’s the reason we’ve not stagnated.”

In the mouth of the average forty-something punk survivor, such words would ring hollow, but the secret history of Sonic Youth shows that the band are above suspicion.

When Sonic Youth formed in New York in 1981, they already straddled the art and rock divide, Moore having played in new-wave band the Coachmen and Ranaldo serving time in composer Glenn Branca’s massed choir of electric guitarists. Seen as spiritual forebears of Nirvana and the grunge movement, which sold punk noise to the MTV generation at the start of the 1990s, Sonic Youth controversially signed to corporate giant Geffen in 1989. Since then, they’ve admirably honoured their more commercial commitments while also jamming and recording with distinguished free-jazz freaks and contemporary composers such as William Hooker or Christian Wolff, issuing their more elliptical music on their own label, SYR. Barefoot in the Head, Moore’s 1988 collaboration with avant-jazz saxophonists Jim Sauter and Don Dietrich of Borbetomagus, was described by alleged sleeve-note writer “Thomas Pynchon” as “two free men meet a slave”. Goodbye 20th Century is the result of Sonic Youth’s two decades’ jangling of the fetters of rock.

Ranaldo explained the album with deference and modesty: “We’d done an improvised show with (free music wunderkind) Jim O’Rourke and (John Cage percussionist) William Winnant in San Francisco. They were very knowledgable about graphically scored work, and we liked the idea of Sonic Youth trying some. So over the next year we put together a shortlist and made phone calls to try to track down scores. They came rolling in and we got excited. Sometimes graphic scores look like music, sometimes they look like Jackson Pollock paintings. Soon we had a big stack of scores to whittle through.”

Sonic Youth’s version of Steve Reich’s 1968 piece, Pendulum Music, was almost something of a coup. “As far as we knew, there wasn’t a recording of it, but a Dutch ensemble beat us to it by a couple of months. Again, it’s a set of instructions – hang the microphones on stands over the amps and pull back and swing until they give out a bleat of feedback. It ends when they’re hanging limp.”

Unlike the band members’ various solo projects, the scary, serious art of Goodbye 20th Century is issued under the Sonic Youth banner, possibly alienating more conservative fans. When Ranaldo and Moore jammed with acorn-shaped jazz horn player Lol Coxhill and British free-noise group Ascension at the Camden Jazz Cafe in 1996, the audience bewilderment was tangible. Ranaldo concedes some anxieties: “People come with certain expectations because our name’s on the bill, but those shows aren’t a one-off thing for us, we’re wholly committed to that area. But we forget sometimes that outside of New York people are very surprised by it. In newsgroups on the internet, people are divided over whether it’s tripe with no songs or the best music we’ve done. Some are totally knocked out, some are totally bummed out. But it’s the right time for this. There’s a generation of younger kids interested in improvised formats. Not all new bands want to be the next indie-rock sensation. They’re as tied to Stockhausen as they are to rock’n’roll.”

Sonic Youth’s millennial rethink follows the theft, earlier this year, of all their instruments from the back of their van. “At the time it was a real drag,” recalls Ranaldo. “All the equipment we wrote the last eight years of material on, with guitars modified to our specifications. We were devastated. But we’re using it to our advantage. It’s forced us to look in other directions, or use guitars from 20 years ago that we’d left to gather dust, and it’s altered our sound.”

At least the stolen instruments will have survived the treatment meted out to the piano featured in the band’s version of Fluxus composer George Maciunas’s 1962 work Piano Piece No13 (Carpenter’s Piece). Computer-literate listeners will find a bonus four-minute video clip included on the first CD, showing the group taking turns to hammer nails into the keys. Drummer Steve Shelley seems a little reluctant, whilst bassist Kim Gordon’s ungainly two-handed grip begs the question: which member of the band is best at putting up shelves?

“I would have to say that I am,” answers Ranaldo without a moment’s hesitation, shattering the illusion of the group’s mutually supportive ethic. “I’m definitely the best.”

Goodbye 20th Century is out tomorrow on SYR records.

For sample graphic scores and Winnant’s essay on the making of the album, visit www.smellslikerecords.com