All of "Ecstasy"s seven tracks were written and composed by Kevin Shields, with Colm Ó Cíosóig credited as the co-writer of three tracks—"The Things I Miss", "Clair" and "(Please) Lose Yourself in Me". Regarding the lyrical content of the album in contrast to the music, Shields said that "the songs may sound sweet, but the subject matter isn't necessarily very nice. A lot of it is relationship-based, but it's always vague, and never just boy-meets-girl. It could easily be boy-meets-boy, or girl-meets-girl. Then there's hate, and whimsical thoughts you get from nowhere". Ó Cíosóig remarked that "it's more weird perversions of feeling you get in a relationship" and referred to the lyrics as being marked by "extremes, because we're entertained by extreme things". Shields noted that the lyrics were a progression from the band's earlier releases as "the idea of composing a sweet pop song that sugar-coated some lyrical horror and sending it hurtling up the charts appealed to our sense of humour" and considered the songwriting process for "Ecstasy" as "fresh after having made pure noise earlier".