The title is a pun on the estuary of the River Forth in Scotland, commonly known as the Firth of Forth. Though the song is credited to the entire band, most of the music was composed by keyboardist Tony Banks. He had written the bulk of the song by 1972, presenting it as a candidate for the albumFoxtrot, but it was rejected. He redesigned the piece, which the group accepted as a candidate for Selling England by the Pound. Banks, who worked on the lyrics with Mike Rutherford, later dismissed them, saying they were "one of the worst sets of lyrics been involved with." The song starts out with a classical-style grand piano introduction played by Banks. This section is rhythmically complex, with certain bars in the rare time signatures of and, alternating with bars of. This section changes tempo and segues into the first section of lyrics, accompanied by Phil Collins on drums and a chord progression between the Hammond organ and guitar. This leads into a flute melody played by Peter Gabriel, followed by a synth-driven instrumental section which restates the opening piano theme. Hackett then plays the flute melody using violin-like guitar tones. Peter Gabriel then sings a brief section of lyrics before Banks concludes the song on piano.
Live performances
From autumn 1973 onwards, the song's piano intro was omitted during live performances. Banks felt he could not play the introduction effectively live, as he used an RMI electric piano on stage, as the RMI was not touch-sensitive. The song survived the departure of Peter Gabriel in 1975, with Phil Collins taking over to sing lead, but was dropped as a piece overall following Hackett's departure in 1977. It was reinstated for the 1981 tour, and performed for the Six of the Best reunion show in 1982. The instrumental section of the song, featuring the guitar solo, was resurrected for the Mama Tour in 1983-84, as well as the We Can't Dance tour in 1992, with touring member Daryl Stuermer playing Hackett's guitar parts. This section of the song featured on the Calling All Stations tour in 1998, with Anthony Drennan playing guitar. It was resurrected for the 2007's ', again featuring Collins and Stuermer. The instrumental segues directly into "I Know What I Like " in 1992 and 2007 versions. Hackett has continued to play the song live since leaving Genesis. It appears on his solo album of re-worked Genesis songs, ', with lead vocal by John Wetton, as well as on Hackett's live album The Tokyo Tapes. The song was also included as an encore on his Genesis Revisited tour, featured on the live album Genesis Revisited: Live at Hammersmith.
Reception
The song has had a strong critical response as one of the best examples of progressive rock. Particular highlights of the track include Banks' piano introduction and Hackett's guitar solo. Rock author Edward Macan describes "Firth of Fifth" as "one of the finest nine and half minutes of music that Genesis ever put down". Genesis biographers Dave Bowler and Bryan Dray describe Hackett's solo as "the crowning moment of Hackett's time with the band." Hackett has spoken favourably about his contributions to the song, saying "it'll always be twinned with me, and I still enjoy playing it. It's a great melody for guitar".
