Heathen was partly a response to the September 11 attacks. Author James E. Perone even stated in his book The Words and Music of David Bowie that the album "chronicles New York City at the time of the...attacks", identifying "Slip Away", "Slow Burn" and "A Better Future" as reflecting a post-9/11 atmosphere. However, Bowie denied any connections to the attacks, stating that all the songs were written beforehand and reflected a general feeling of anxiety that he had accumulated living in America, particularly "Slow Burn". Nevertheless, he admitted that "Sunday" "was quite spine-tingling to realise how close those lyrics came. There are some key words in there that really just freak me out." Visconti later explained that the recording sessions were still underway at the time of the attacks, but suggested that "only a few lines were amended after September 11". Plati also commented that "I think in Heathen you can feel the overall mood of where we all were during those times." Songs Album opener "Sunday" displays pervading electronic textures and synthesiser-based loops, musically descending from the atmospherics of Low and tracks such as "Word on a Wing" (1976), "The Motel" (1995) and "The Dreamers" (1999). Establishing the album's core themes of spiritual doubt and existential dread, the dreary lyrics were inspired by the surrounding region around Allaire. Regarding the title, Pegg evaluates it as "neatly encapsulat[ing] the album's sense of an uneasy balance between the spiritual and the secular." "Cactus" discusses a distaste and lack of sexual engagement that represents a departure from the album's main themes. Featuring Visconti on bass and Bowie on all other instruments, including his only recorded drum performance, Pegg considers the rendition a raw, tightly produced piece of garage rock that pays homage to T. Rex's "The Groover" (1973). "Slip Away" is a ballad reminiscent of "Space Oddity" (1969) and "Life on Mars?" (1971). Rewritten and remade from the Toy track "Uncle Floyd", the lyrics meditate on lost happiness and yearning expressed through the views of two puppets from the obscure low-budget children's television series The Uncle Floyd Show. Bowie, who appeared on the show in 1981, said in 2002 that he placed "Slip Away" on Heathen because he "wanted something on the album that pointed to a nicer time... even if it wasn't necessarily true." "Slow Burn" musically harkens back to his 1970s works, particularly with saxophone playing; Pegg finds it a