It's tempting to hope that The Beatles' fabled 14-minute track "Carnival of Light", which Paul McCartney wants to release 41 years after its recording, will be a magnificent avant-garde assemblage of noise.
But the truth is that just because it was John, Paul, George and Ringo wandering around the studio banging things and shouting "Barcelona!" doesn't mean the result will be a masterpiece, no matter how often McCartney mentions Karlheinz Stockhausen. It was never released because the other Beatles thought it "too adventurous". This is the same band that would release such fare as "Revolution 9" on The White Album, so chances are that "too adventurous" was their way of gently letting Paul know that "Carnival of Light" was a bit rubbish.
The track, laid down in 1967 between sessions for "Penny Lane", is far from the only "lost" recording that has achieved mythical status. Guns N' Roses' new album, Chinese Democracy, is one case; after 14 years and $10m, Axl Rose's opus is bound to disappoint when it's finally released next week, whatever its quality. Perhaps Rose - and McCartney - would be better off leaving their legendary lost tracks in the drawer.
They'd be in good company. With Dark Side of the Moon blowing the world apart in 1973, Pink Floyd supposedly returned to the studio to record an album using only home-made instruments - rubber bands, kitchen utensils and the like. The project was soon abandoned and the tapes remain blessedly undiscovered. Bruce Springsteen's 1982 acoustic album Nebraska is made up of home demos for an electric LP he recorded with the full E Street Band. The Boss decided - rightly, we must assume - that the demo was the better version, and released that instead. "Electric Nebraska" has never been heard.
After the success of The Who's rock opera Tommy in 1969, Pete Townshend set to work on his own never-released conceptual masterwork, Lifehouse. Drawing on his obsessions with sci-fi and spirituality, Townshend constructed a dizzying plot set in a dystopian 21st-century Britain. To play Lifehouse live, the songwriter decided he would invent an interactive musical computer that could digest biographical data from audience members and play each of them a personalised gig. Before he could complete the ambitious project, however, he had a nervous breakdown. He abandoned Lifehouse and dumped most of the extant tracks on to subsequent Who albums. The six-disc Lifehouse Chronicles, released in 2000, is a curio for hardened fans only.
The most notorious album-dodger is Neil Young, whose famed "Missing Six" albums (including On the Beach) weren't released on CD when the format became standard - two are still "missing". His 1975 album Homegrown was finished and the cover art designed before he decided to shelve it in favour of Tonight's the Night. Though some tracks from Homegrown made it on to later albums, the completed record remains under lock and key.
But perhaps the greatest lost LP of all also became the most successful when it was finally released. Brian Wilson had a breakdown while writing and recording Smile, the follow-up to The Beach Boys' masterpiece, Pet Sounds, in 1967. Smile, his "teenage symphony to God" (which included "Good Vibrations"), was eventually completed with the help of Wilson's new backing band, The Wondermints, in 2004, and rapturously received. McCartney must have been listening; in 1967, Wilson's sceptical bandmates told him it was risky to tinker with their hit-making formula. Smile, they told him, sounded "too adventurous". And what did they know?