McCartney said while the rare track was thought to have been lost after his fellow Beatles members deemed it too adventurous at the time it was written, he is determined to finally unveil "Carnival" to the public, The Observer reported Sunday.
"It does exist," McCartney said of the track.
"Carnival" was recorded by McCartney, Ringo Starr, George Harrison and John Lennon in 1967 after McCartney lobbied his band mates.
"I said to the guys, this is a bit indulgent but would you mind giving me 10 minutes? I've been asked to do this thing," McCartney reminisced. "All I want you to do is just wander round all of the stuff and bang it, shout, play it."
Journalist John Wilson told The Observer McCartney will release the track, which was created for an electronic music festival, if he receives blessing from Starr, Harrison's widow Olivia and Lennon's widow Yoko Ono.