The duo wrote, produced, and played instruments on the tracks, while Heap also provided lead vocals.

[3][4] As Heap went on tour throughout North America and Europe to promote the album, Sigsworth continued to write and produce for other artists, including Madonna and Björk.

An album of electronic music with elements of trip hop, pop and rock, the eclectic, intricately produced tracks use a wide range of traditional instruments including cellos, autoharps, guitars, keyboards, and Indian drums, with layered vocals from Heap.

[11] The follow-up singles "Must Be Dreaming" and "It's Good To Be in Love" were shelved from commercial release in the UK, however, through lack of radio and TV interest.

"Breathe In" and "Must Be Dreaming" did become minor hits in Asia, particularly in Indonesia, where both singles made Top 10, peaking at number 7 and 5 respectively on the Indonesian Airplay Chart.

The track was written by Sigsworth, Swedish pop star Robyn and her long-term songwriting companion, and Sigsworth asked Heap to come in and make the song more suitable for Spears, adding backing vocals and making the track more electronic music-infused.

Despite not being used on In The Zone, the track was released in late 2005 on the Japan CD single of Spears' single, "Someday (I Will Understand)" and on the UK and Japan bonus CDs of the DVD release of her reality TV show, Britney and Kevin: Chaotic.