"Firth of Fifth" is a rock song by progressive rock band Genesis, from their 1973 album Selling England by the Pound. The title is a pun on the estuary of the River Forth in Scotland, commonly known as the Firth of Forth.
The song starts out with a classical-style grand piano introduction by Tony Banks, before switching tempo toward the first section of lyrics, accompanied by drums and a chord progression on the organ. The song then features a flute melody, followed by a synth-driven instrumental which restates the opening piano theme. Steve Hackett then plays a solo (an interpretation of the flute melody) using one of his signature violinesque guitar tones. Peter Gabriel then sings a brief section of lyrics before Banks concludes the song on piano.
At over nine minutes long, this song is representative of Genesis' work during their progressive rock period. It is also one of the band's most popular early works, and is featured on their second compilation album, Platinum Collection (2004).
Although "Firth of Fifth" is credited to the entire band, Tony Banks would later claim that much of the music was developed from his own ideas (the flute and guitar solos were interpretations of a melody that Banks wrote on piano.) Banks also wrote much of the lyrics. He would later state in Hugh Fielder's The Book of Genesis that it was one of the worst sets of lyrics he had been involved with.
After 1975, the song's piano intro was omitted during live performances. Tony Banks had used an RMI electric piano instead of a proper piano on stage, and he found it difficult to play the intro with the limited properties of the RMI.
The song appeared in instrumental form (the middle keyboard and guitar solos) as part of the 1992 We Can't Dance tour and 1998 Calling All Stations tour, as well as in 2007's Turn It On Again: The Tour. The instrumental segues directly into "I Know What I Like (In Your Wardrobe)" in 1992 and 2007 versions.
It also appears on Steve Hackett's solo album of re-worked Genesis songs, Watcher of the Skies: Genesis Revisited (1997).