Sir Paul McCartney announced that a "lost" Beatles track recorded in 1967 and performed just once in public could finally be released. The song is called "Carnival of Light," a 14-minute experimental track the Beatles recorded in 1967 but never released.

It appears the band played the recording for an audience just once, at an electronic music festival in London. It reportedly includes distorted guitar, organ sounds, gargling and shouts of "Barcelona!" and "Are you all right?" from McCartney and John Lennon. But in order to enable it to be made public, McCartney needs the approval of Ringo, as well as the widows of Lennon and Harrison, Yoko Ono and Olivia.

“It does exist,” McCartney says on a BBC Radio 4 arts programme to be broadcast this week. Talking to John Wilson, the presenter of Front Row, the former Beatle confirms that he still has a master tape of the work and says he suspects that “the time has come for it to get its moment… I like it because it's the Beatles free, going off piste,” he adds.

Although it was performed at an electronic music festival that year, the audience were unaware it was a Beatles track and the band later shelved it, feeling it was too adventurous. George Harrison had called such experimentation "avant-garde a clue", McCartney said. But the track gained legendary status among hardcore Beatles fans.

Sir Paul was commissioned by his friend Barry Miles to make a track for the 1967 Million Dollar Light and Volt Sound Rave at the Roundhouse Theatre in London. Drawing inspiration from the composers Karlheinz Stockhausen and John Cage, "Carnival of Light" was duly recorded at the Abbey Road studios while the band was working on the vocals for "Penny Lane".