The album blended dream pop and ambient pop with elements of psychedelia and experimental and electronic textures. The composition of Heaven or Las Vegas reflected a shift toward more accessible and structured songwriting, balancing the band's established ethereal textures with clearer melodies and rhythms. Built around Robin Guthrie's guitar work, Simon Raymonde's bass lines, and programmed percussion, the songs incorporated brighter harmonies and major–minor chord progressions that conveyed both intimacy and emotional depth. Elizabeth Fraser's vocals, while still marked by glossolalia and unconventional phrasing, were delivered with greater clarity than on previous albums, a change often linked to her personal circumstances at the time.
Despite signing a major label deal with Capitol Records, the band declined to promote it extensively but nevertheless shot a video for "Carolyn's Fingers", which was issued as a single in the United States. The band brought on a manager for the first time as they had run into tax trouble previously. The band took on new familial responsibilities as bassist Simon Raymonde married his first wife, Karen, and vocalist Elizabeth Fraser was expecting her first child with guitarist and co-founder Robin Guthrie. The latter's cocaine habit previously "escalated" during the recording process for Blue Bell Knoll; Fraser and Raymonde believed that the new baby would prove a diversion from Guthrie's dependency and allow the pair to "play happy families". Their wishes did not pan out, with Guthrie relying heavily on drugs as the band developed Heaven or Las Vegas, causing him to experience "deep" paranoia and mood swings.
The recording sessions took place at Eel Pie Studios (then September Sound) in Twickenham, London. According to Gary Walker, the environment was "overshadowed by the transience of death, birth and heartbreak". In September 1989, Fraser and Guthrie's child, Lucy Belle was born; Heaven or Las Vegas was released on her first birthday. Of her pregnancy, Fraser said that she gained clarity about what mattered to her most: "Suddenly I had confidence which I'd never ever had in my life, which I consequently lost after I had the baby, because it's such a frightening experience you lose it again and you have to start over again. But it does change you". Raymonde's father, Ivor Raymonde, died shortly after Lucy Belle's birth, as the band were in the middle of recording. His passing cast what Raymonde called a "dark cloud" over the sessions.
The album's drum programming was done by Guthrie, the first step in every Cocteau Twins recording session. Guthrie and Raymonde constructed the music before Fraser recorded her vocals. Raymonde likened Guthrie's rhythms on the album to hip-hop beats; despite their music being far removed from it, he acknowledged that it came from a "dance-y" place. Many of the "mysterious" instrumental effects on Heaven or Las Vegas were achieved by accident, using guitars rather than "omnipresent" synthesisers. As a result of Guthrie's decreased time in the studio, Raymonde's playing was more notable and he became more involved in the recording process.
Oftenly categorised Heaven or Las Vegas as a dream pop and ambient pop recording. The album carries psychedelic, experimental and electronic textures. Heaven or Las Vegas displays musical evolution, with the music becoming more accessible, "warmer, and more inviting". During the band's narcotic periods, their music became more "ecstatic". They began incorporating syncopated, "danceable" rhythms and immersive synthesiser textures. Guthrie's guitar work has been described as "chiming", Raymonde's bass work has been described as "ominous and pulsing" and Fraser's vocals have been described as "mesmeri[s]ing", along with her high notes have been characterised as sounding "angelic".
The album's songwriting was also improved, with tracks blending major and minor chords to create a more tangible emotional depth. Heaven or Las Vegas straddled the two themes: "writing songs about birth, and also death, gave the record a darker side that I hear in songs like 'Cherry-Coloured Funk' and 'Fotzepolitic'". Despite being in a "very good space musically" and describing the recording process as an "inspirational time", Raymonde said: "It was trying to mask all the other shit that was going on that we didn't want to stop and think about for too long". In a retrospective of 4AD by music journalist Martin Aston, he noted that Fraser named the album Heaven or Las Vegas as "a suggestion of truth versus artifice, of music versus commerce, or perhaps a gamble, one last throw of the dice". Many of the song titles were described as "vague" and "nonsensical as ever" such as "Iceblink Luck", "Fotzepolitic" and "Frou-Frou Foxes in Midsummer Fires".
The opening track, "Cherry Coloured Funk", is characterized by a straightforward beat, a heavier bass line, a minimalist three-chord hook, and a "melt-in-your-ear melody". "Pitch the Baby" is a track that has hip-hop elements and reflects on the experience of childbirth and the joy of welcoming a child, with many of the album's songs centering on Fraser's newborn daughter, Lucy Belle. "Iceblink Luck" retained its lush, velvety texture in performance, with Elizabeth Fraser singing chiefly in her lower register. "Fifty-Fifty Clown" was built without the use of synthesisers, despite featuring textures that may resemble them. While experimenting with a newly acquired piece of rack-mounted effects gear, Raymonde plugged in his guitar to assist Guthrie in exploring its capabilities. Guthrie subsequently added additional guitar layers, and the band initially considered the instrumental version complete. However, once Elizabeth Fraser contributed her vocals, Raymonde described the result as "divine". According to Raymonde, the title track "Heaven or Las Vegas" featured Fraser's idiosyncratic vocal style, particularly her backing vocals, which he considered especially "underrated". The band was confident in the instrumental arrangement, but Fraser's vocal performance elevated the song during the recording process.
"I Wear Your Ring" was likened to a "postmodern Karen Carpenter", with lyrics delivered in an unusually clear manner. "Fotzepolitic" blended jangling folk-rock guitars with another warmly delivered Fraser vocal. "Wolf in the Breast" is described by Raymonde as one of his personal favourite tracks on the album. He recalls it as a deeply emotional piece that continues to move him, particularly due to the interplay between his bass lines and Guthrie's guitar work, and described the composition as one that "writes itself". Fraser's voice conveys a sense of vulnerability in "Road, River and Rail", occasionally cracking with emotion. Raymonde wrote "Frou-Frou Foxes in Midsummer Fires" the day after his father's death.
About the album cover, the band wanted a visual representation that would capture "the ethereal", according to Guthrie. Paul West, of the design studio Form, previously worked with Cocteau Twins on the cover for Blue Bell Knoll. West recruited photographer Andy Rumball, and the pair experimented with various materials to generate a "textural and otherworldly" effect. The final artwork is a long exposure of Christmas tree lights against a colour backdrop, with its typography produced by hand on an acetate overlay.
