The song was performed at an electronic music festival that year and the audience was ignorant that it was a Beatles track. However, the band never released it, thinking the song was too adventurous. McCartney said that George Harrison had called such experimentation "avant-garde a clue".
Macca possesses a master tape, and said, "the time has come for it to get its moment", if he can get permission from the group's estate for its release. McCartney 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. Taking 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," the Independent quoted McCartney, as telling 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," McCartney said. Sir George Martin, the producer who oversaw the recording, described the track as 'a kind of uncomposed free-for-all melange of sound'.