Carnival Of Light
This is a rare case of lostwave music having it's history known, just the actual song is missing. The song was a request made to Paul McCartney in December of 1966. He was asked to make the song for an upcoming festival in Londen occuring between the 28th of January and the 4th of February called A Million Volt Light and Sound Rave. This event was comprised of light shows, experimental music, and other more abstract things.
McCartney agreed to create the song and recorded it the next month for the event. The song did indeed play at the event (as confirmed by many attendees and organizers) and the light designer for the event took the tape with him to the United States, however this man passed away in 2016 with no idea if he still had the tape all those years later.
A book called Here, There, and Everywhere: My Life Recording the Music of the Beatles by Geoff Emerick states that portions of Carnival Of Light were reused for White Album track Revolution No. 9, however this has never been officially confirmed. McCartney tried to release the track in 1996 on the compliation record The Beatles Anthology 2 but Georgie Harrison voted against it so it did not make the final cut. The same year McCartney had intended to use the song in a collage film he was making, however nobody has seen this film and the last anyone heard of the collage film was in 2002. McCartney mentioned in a November 2008 interview that he was looking to release the song but needed consent from the estates of the other members to do so. The last mention of this song was in a September 23rd, 2013 interview with Jimmy Kimmel where McCartney briefly described the song. The song still remains unreleased, however, recreations exist online of what the song might sound like.
Recreation of the song