“FX” came from a joke. After smoking weed, the crucifix hanging from Iommi’s neck accidentally struck the strings of his guitar and the band considered it an interesting sound. An echo effect was added and the band proceeded to hit the guitar with various objects to generate odd sound effects.
Lyrics for this song have yet to be released
FX was written by Bill Ward & Ozzy Osbourne & Tony Iommi & Geezer Butler.
FX was produced by Tony Iommi & Patrick Meehan.
Black Sabbath released FX on Mon Sep 25 1972.
[The song is] a total joke.
—Tony Iommi