… is about to produce a typical burst of Beatles-related hyperbole. (Reuters: “Mythical Beatles song to be released.”)

It’s not mythical and it really isn’t a Beatles song. It was a ten-minute-plus sound-effects tape Paul McCartney marshaled together for an art festival at a London theater. In Mark Lewisohn’s history of the group’s recording sessions it’s clear the project was so unlike a song that it it exasperated George Martin. (”This is ridiculous, we’ve got to get our teeth into something a little more constructive.”)

But there are a few interesting things about it. One, it’s apparently never been bootlegged, though it still resides in the Abbey Road archives. According to Lewisohn, McCartney packed the track off to deliver it to the fest organizers, but he apparently held on to a copy, too.

Of course any unreleased Beatles track is of intrinsic interest. What the potential release of the song at this point is about, however, is yet another lingering example of McCartney’s bruised ego about having his aesthetic reputation overshadowed by the work of “the experimental one,” John. “Carnival of Light” was put together a year and a half before Lennon’s  “Revolution 9,” the group’s sole contemporary excursion, leaving aside the Christmas releases, into something approaching avant-garde song construction.

McCartney thought he lead the group into adventuresome musical territory, and wasn’t above noting that Lennon had been living “out in the suburbs by the golf course with Cynthia” (Lennon’s first wife) while he, McCartney, was grooving with the real avant-gardists of the time.

You can get a sense of McCartney’s understanding of avant-gardism as Billboard quotes him describing the song’s genesis:

“I said [to the other musicians] 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.”