Hidden tracks can appear at the end of a CD, usually after a long gap of silence, and don’t appear on the track listing. They’re a fun surprise for listeners.

• The first ever “hidden track” was on a vinyl record. At the end of the Beatles’ Abbey Road, there’s 14 seconds of silence, followed by the 30-second song “Her Majesty.” The song was supposed to go elsewhere on the album but Paul McCartney hated it, so he asked tape operator John Kurlander to trash it. He didn’t—he secretly placed it at the end of the album without telling anybody.

• The Clash’s “Train in Vain” is the last song on its 1979 album London Calling, but it’s unlisted. The band wanted to include it at the last minute, after the record sleeves had already been sent to the printer.

• It didn’t really catch on until the compact disc format took hold, which made hidden tracks that much easier to hide—unlike a record, that extra track was visually invisible. Hundreds of acts did it in the ’90s, a fad started by Nirvana. Its 1991 album Nevermind contained a hidden track called, appropriately enough, “Endless, Nameless.”

• In 1995, rock band Boris the Sprinkler included a hidden track on its album Saucer to Saturn: the entirety of the album again. They did it so fans could theoretically listen to the entire album on a jukebox for the cost of playing one song.

• The alternative rock band Cracker had one of its biggest hits with “Eurotrash Girl” in 1994. They wanted to include it on their album Kerosene Hat, but their record label told them the record was already too long…so the band snuck it in as a hidden track.

• First hidden track with a Grammy nomination: Lauryn Hill’s cover of “Can’t Take My Eyes Off Of You” was a hidden track on The Miseducation of Lauryn Hill, was nominated for Best Female Pop Vocal Performance in 1999.

• The Ramones’ “Carbona Not Glue” is a hidden track on its Loco Live album. The makers of Carbona stain remover objected, so it was removed from the track listing on the album cover, but the actual music remained on the CD.

• The whole point of a hidden track is that it’s hidden, but in 1995, the Rembrandts had to ironically advertise a hidden track on its album LP. The band had done the theme song for Friends, and it became a huge hit just when LP was being pressed, and after the album covers had been printed. So, early versions of the album contain a big sticker advertising the album’s hidden track, the band’s theme from Friends.