To demonstrate, guitarist Ritchie Blackmore grabbed an acoustic guitar and began playing a riff consisting of a single "G" repeated over and over, while vocalist Ian Gillan improvised lyrics over the top.

[7] The song first appeared on the 1972 LP Machine Head and remained one of the band's live concert staples, being the set opener even before it was released on any album.

Record World said of the U.S. single release, "This mover has a Led Zeppelin tint to it, and that could bring group back to the top of the pops.

The Guardian said, "Blackmore’s playing is like a force of nature on the Made in Japan version; those slashing chords in the intro, and that amazing solo featuring the distinctive neo-classical descending runs, combining the spirits of Bach and Jimi Hendrix.

This part consists mostly of fast, arpeggiated notes with a late Baroque/Early Classical influenced feel and makes use of the harmonic minor scale.

[16] Other bands to record the song include Dream Theater, Point Blank, Stryper, Metal Church, Buckcherry, Type O Negative, Faith No More.