Preliminary songwriting for
A Bath Full of Ecstasy was undertaken by Hot Chip members
Alexis Taylor and
Joe Goddard, and first traces back to work they did for
pop singer
Katy Perry. After she asked them to help with songwriting for her 2017 album
Witness, the duo spent four days at
Air Studios collaborating with her. Goddard called it "incredibly exciting" and said: "I loved writing for somebody else. She was great, very funny and easygoing". One of the songs they wrote, "Into Me You See", ended up on her album, while two others, "Spell" and "Echo", were re-worked by Hot Chip for
A Bath Full of Ecstasy. Felix Martin said, "We ended up with the leftover bits they'd written, being very much obvious pop stuff, and those songs ended up being something more interesting than that." Taylor and Goddard also recorded
demos at Goddard's studio in East London. When the members of Hot Chip re-convened to record
A Bath Full of Ecstasy, they decided to work with outside producers for the first time and to allow them to have a say in the songwriting. The two producers had very different styles. McDonald, who Martin described as "mild-mannered", "analytical", and "goal-oriented", brought a pop-centric mindset and deliberated about the song structures. He recommended to the group where to add
bridges,
choruses, and
hooks, how many
bars they should last, and he considered how the songs should be edited differently for radio or streaming services. Martin said the producer was very honest and never afraid to suggest changes if he thought the songs could be improved, Contrasting with his counterpart, Zdar believed in long edits of tracks instead of making short pop songs. Taylor said Zdar had a knack for spotting the vocal melodies and hooks in songs, and his mixes emphasised them while also giving "more space in the music". Taylor also enjoyed the unfamiliar equipment and instruments that Zdar offered the group, helping them deviate from familiar habits. Goddard called him "bold and passionate" and praised his skills at "working with bass, making records feel really full and alive". He said the producer's "sense of joy and wonder at the world" helped instill the group with more confidence. They worked with Zdar at his studio, Motorbass Studios, in
Montmartre, Paris. Goddard credited the band members' musical pursuits outside of Hot Chip with improving them as a band, saying that they honed their skills "either as a musician or a producer, an arranger or a live player". He cited Doyle as an example, saying he had strengthened his guitar and bass guitar playing due to his experience performing with
LCD Soundsystem on tour. Approximately 20 songs were in consideration to be included on the album. Martin said that if decision of the track listing has been left entirely to the band members, the album would have comprised 10–12 songs, but they received advice from the record label and producers to keep it more concise. ==Release and promotion==