A 14-minute, improvised, experimental track recorded by the Beatles which was considered unworthy of being issued under their name may be released 41 years after its only public performance, Sir Paul McCartney has revealed.

"Carnival of Light", which the band laid down in January 1967, features distorted guitars and drum-beats, gargling, church organs, and Sir Paul and John Lennon yelling: "Are you all right?" and "Barcelona!"

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.

The track gained legendary status among hardcore Beatles fans, and Sir Paul has not only confirmed that he possesses a master tape, but said "the time has come for it to get its moment", if he can get permission from the group's estate for its release.

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 were working on the vocals for "Penny Lane".

"We were set up in the studio and would just go in every day and record," Sir Paul told the BBC Radio 4 arts programme Front Row, in an interview to be broadcast later this week.

"I said to the guys, this is a bit indulgent, but would you mind giving me 10 minutes? All I want you to do is just wander round all the stuff and bang it, shout, play it. Then we put a bit of echo on it. It's very free." The track came within a whisker of inclusion on the 1996 Beatles compilation Anthology. "I said it would show we were working with really avant-garde stuff, but it was vetoed," Sir Paul said.

The producer who oversaw the recording, Sir George Martin, described the track as "a kind of uncomposed free-for-all melange of sound".