in December 2005, Utada talked about the process: Utada first completed the lyrics to "Sanctuary" as they felt it was easier than writing it in Japanese. Furthermore, they said that they found it difficult to write the lyrics for "Passion". Retrospectively, Utada stated to Oricon Style that both of the songs' lyrics were some of their favorite lyrics to date. Knowing that the compact discs of the single would be insufficient with the lack of additional material, they decided to create a B-side track that was identical to the first song; this was titled the "After the Battle" version, the composition played during the credits of the game. They traveled to West Hollywood, California, to record their vocals at Westlake Audio Studios with Pat Woodward, whilst the Japanese version was recorded at Bunkamura Studios, Shibuya, Tokyo with Matsui Atushi. Additionally, they re-recorded her vocals for the "After the Battle" version in order to blend it with its new arrangement. The tracks were produced by Utada, with additional production credits to Akira Miyake and Utada's father Teruzane. Composition "Passion" is composed as a multi-genre tune that emphasizes the core elements of alternative rock, ambient and ethereal music. MuuMuse's Bradley Stern asserted that "Passion" was Utada's "most complex" recording, noting the use of "passionate drumming" and ambient sounds. He described Utada's vocals as having an "ethereal"-like vibe. David Jeffries of AllMusic compared it to "A Whole New World" and the work of Nine Inch Nails. With instrumentation of drums, keyboards, electric guitars and synthesizers, the track was distinctive for its overuse of echoing throughout the composition. Additionally, critics noticed the overlapping technique of Utada's singing, along with the use of reversing certain sections of her voice to hide messages within the song. According to the sheet music on Musicnotes.com, which was published by the BMG Rights Management and Walt Disney Music Publishing, the recording is composed in the key note of F♯ major. It is set in time signature of common time with a tempo of 109 beats per minute, whilst its chord progression develops in the sequence of B♭m7–Dm7–B♭m7–Dm7–Dm7–Dm. "Passion"'s lyrics delve into themes of nostalgia, and discuses the circumstances of past, present and future, which she noted was relatable to the characters in the video game. However, Yahoo! Music's Miko Amaranthine said "Passion" is "another love song that resembles a missing love but leaving life without him/her." Furthermore, "Passion", "expresses