Paul McCartney is itching to release the most experimental track the Beatles ever put to tape -- but he'll need the permission of Ringo Starr and the estates of George Harrison and John Lennon to do it.

McCartney told BBC Radio 4 of "Carnival of Light," a 14-minute piece recorded in early 1967, "the time has come for it to get its moment" and that it shows the Beatles "going off piste."

"I said it would be great to put this on because it would show we were working with really avant-garde stuff," he said of the recording, which has never been bootlegged.

"Carnival of Light" was recorded for the electronic music festival the Million Volt Light and Sound Rave and received its only public play there in early '67. McCartney tried to include it on the Beatles' "Anthology" in the late '90s but was vetoed by Harrison.

"I said all I want you to do is just wander around all the stuff, bang it, shout, play it, it doesn't need to make any sense," McCartney said of the music. "Hit a drum then wander on to the piano, hit a few notes, just wander around. So that's what we did and then put a bit of an echo on it. It's very free."

A handful of Beatles experts have heard the song, the master tape of which McCartney purports to have.

Author Mark Lewisohn says the song features "distorted, hypnotic drum and organ sounds, a distorted lead guitar, the sound of a church organ, various effects (water gargling was one) and, perhaps most intimidating of all, John Lennon and McCartney screaming dementedly and bawling aloud random phrases like 'Are you alright?' and 'Barcelona!'," while Barry Miles has described it as similar to the Frank Zappa song "The Return of the Son of Monster Magnet."