The Call of Ktulu is the closing track for Metallica's second album Ride the Lightning. The song is a lengthy instrumental and is the longest song on the album. It is the last Metallica song that had any contribution from former guitarist Dave Mustaine, who was kicked out before the band recorded their first album.
The song appears on a 1983 four-song demo for Ride the Lightning. Like the album, the demo closes with the instrumental, which was named "When Hell Freezes Over" at the time. The song was often played much faster live than the finished version.
The current title of the song is named after author H.P. Lovecraft's most well-known story, the Call of Cthulhu. Lovecraft was introduced, along with his book "The Shadow over Innsmouth", to the rest of the band by Cliff Burton; the latter song inspired the Thing That Should Not Be, written by Burton. In Lovecraft's stories, Cthulhu is a powerful, God-like alien from another dimension, who is worshipped by cults on earth who believe it is a demonic God - the song has various demonic growls and noises throughout.
- The Call of Ktulu was first performed on August 28, 1983, in Las Cruces, New Mexico, being the first song off of Ride to be played live.
- As of August 2016, it's been played 81 times live.
- From it's live debut in 1983 to just before Ride the Lightning came out, Ktulu was known under it's demo name When Hell Freezes Over, it was changed to it's current title after a conscious effort by the band to not sing about demons and hell as many other metal bands did at the time.
- "The Call of Cthulhu" first appeared in 1928 for the magazine "Weird Tales".
- Despite the song title, the creature's name is actually spelt "Cthulhu", which is pronounced "Ktulu". Various reasons have been suggested for this; one being that according to the story, mentioning "Chthulu" by name (or writing his name) will summon him; another is that the title is to help people pronounce the word correctly
- The edited beginning of the song was later used on Megadeth's last song on album "The World Needs A Hero" called "When", in 2001.