Fire in My Heart

Themes and recording

The track was originally called "Heartburn", a name Gruff Rhys felt was more poignant and gave the song "a twist", but other band members were unhappy with the title so it was changed. Rhys described it as a country and western song written with absolute sincerity despite clichéd lyrics, offering "soul advice" about "all kinds of people in your life". Recorded in mid-1998 at Real World Studios in Box, Wiltshire, alongside the rest of Guerrilla, the song was produced by the band. B-side "The Matter of Time" was considered for the album but omitted to avoid self-indulgence; the band instead included "The Teacher", a decision Rhys called decisive.

Composition

"Fire in My Heart" runs for two minutes and forty-five seconds in E major. Gruff Rhys starts the first verse alone with a finger-picked acoustic guitar. At thirty-one seconds, the second verse brings in sparse drums, a synthesizer, organ, and harmony vocals. The third verse features louder drums, leading to a bridge at one minute and thirty-one seconds where Rhys asks about a monkey puzzle tree and a fire turning blue. A key change to F♯ major introduces the final verse, where Rhys repeats "I've got a fire in my heart for you" with layered harmonies. The song closes with a coda stretching the word "you" over A♯ minor, A, G♯ minor, and F♯ chords.

Release and critical reception

Released on 9 August 1999 across CD, cassette, and 7-inch formats, "Fire in My Heart" climbed to number 25 on the UK Singles Chart. The track later appeared on the band's 2004 greatest hits collection Songbook: The Singles, Vol. 1. Melody Maker praised it as a "lovely song, a real scarf-waver," though they wished the band had been "howling at the moon in their more deep-throated manner." Guest reviewer Caprice compared it to Carole King and Rickie Lee Jones, calling it "just about the words" and the kind of music that "never goes out of fashion."

NME labeled it a "bizarre psychedelic-folk-gospel record" that confirmed the band as the best British singles band "in ages and ages," later ranking it 35th on their singles of the year chart for 1999. Yahoo! Music deemed it a heartbreaking song of "staggering genius." Mojo described it as "trad-sounding" four-chord folk, while Pitchfork noted its "country endearments."

The BBC called it an "idiosyncratic love song." It placed 17th in the 1999 Festive Fifty on John Peel's BBC Radio 1 show.

Music video

The promotional music video, directed by Jake & Jim (who also directed the video for subsequent single "Do or Die"), shows the Super Furry Animals waiting to leave Mars after playing a concert there. It begins with Gruff Rhys standing alone on Martian soil as a silver, computer-generated spaceship lands behind him. Around one minute in, the camera reveals the rest of the band sitting to Rhys's left: guitarist Huw Bunford on the floor playing acoustic guitar, the others on three connected metal seats.

Two aliens walk from the spacecraft toward the band; one, with a bald head, sunglasses and pointy ears, places a hand on Rhys's shoulder. Rhys turns to look at the other alien, which has one eye in a large round face and wears a blue hoodie. The alien smiles, and Rhys looks up to see Earth in the sky. Drummer Dafydd Ieuan and keyboardist Cian Ciaran also look at Earth before the camera reveals hundreds of aliens waving in front of minaret-like towers.

The band picks up a suitcase and guitar and walks toward the spaceship. The aliens were designed by regular collaborator Pete Fowler, who acted as creative advisor. According to Rhys, the aliens were animated by the same special effects team that worked on Star Wars: Episode I – The Phantom Menace. Rhys considered his performance "wooden" due to a stiff neck requiring painkillers during the shoot.