Music The album marked a departure in Fall Out Boy's sound in which the band implemented a diverse array of musical styles. As reported by
Billboard, Fall Out Boy "drifts further from its hardcore punk roots to write increasingly accessible pop tunes," a slight departure from the group's previous more
pop-punk sound.
Infinity on High has been compared to the work of
pop-punk bands such as
Green Day, with Ann Powers of the
Los Angeles Times commenting, "Whatever snot and feedback courses through these songs, sweetness always triumphs, carried forth by
bubblegum bass lines, snappy drums and tunes as comforting as lullabies." Stump explained that the album contains a variety of different moods: "It’s one of those things where you get older as a band and you do your own thing...The older Fall Out Boy elements, from the early records, are definitely there, and this album is an extension of that." and which itself led with a spoken introduction from
Jay-Z, who owned the record label that produced the album,
Def Jam Recordings. In an interview with Fall Out Boy, drummer
Andy Hurley stated that the opening parts in "Thriller" were copied from "Islands to Burn" by
Racetraitor, a band he once drummed for. The song was created as an reflection on the band's previous two years. Some lyrics reflect on previous mediocre album reviews the band received. The lyrics also call out the rise of the band's popularity, "But by fall we were a cover story". In context the song's opening lines are, "Last summer we took threes across the board, but by fall we were a cover story now in stores. Make us poster boys for your scene, but we are not making an acceptance speech." The song also features the lyric "Fix me in
45" which refers to the way
singles were released on
vinyl records. Some reviewers complained that the album did not have a hardcore edge, but the song "Thriller" was an exception.
Alternative Press opined in February 2023 that the song was dominated by the soaring vocals of
Patrick Stump and his
pop arrangement, and described it as the tenth heaviest song in the Fall Out Boy body of work. Writing in August 2023, Tamzin Kraftman wrote that the song's "chugging pulse", played by Fall Out Boy guitarist
Joe Trohman, "electrifies the track". Stump called "
This Ain't a Scene, It's an Arms Race" the "
funkiest thing we’ve ever done", and attributes the change in musical style to his love of
soul music, which he acquired by listening to oldies stations as a child. Wentz describes the song "a bit of '70s funk mixed with [the band’s 2003 album]
Take This to Your Grave with tight verses and big, fat choruses". The song closing sing-along was influenced by
Justin Timberlake's "
Señorita". Cory Apar of
Allmusic compared the
Babyface-produced track "
I'm Like a Lawyer with the Way I'm Always Trying to Get You Off (Me & You)" to
Maroon 5. The song features Stump singing in a
falsetto in the chorus over Trohman's "crunchy" guitars, as well as a breakdown in which Wentz employs
death growl-style vocals. Violins are used on both "Thnks fr th Mmrs", in addition to an
acoustic guitar strummed
flamenco-style, and "The (After) Life of the Party", which also features
electronic-influenced sounds. Commenting on the instruments used on "Thnks fr th Mmrs", Stump stated "I never thought I'd get a
euphonium onto a Fall Out Boy record". Barry Nicolson of
NME referred to the song as a "towering,
Foo Fighters-esque slice of thunderous rhythm and radio-friendly melody." Critics have described the album as being a
pop-punk,
pop rock, album.
Lyrics was lyrically inspired by rapper
Lil Wayne on the album. While writing the album, Wentz drew lyrical inspiration from rapper
Lil Wayne, whom he called "the best lyricist of [2006]." Critics felt that much of the lyrics address the band's rise to fame and the pressure of maintaining a loyal fanbase. Sasha Frere-Jones of
The New Yorker commented that "The only top-ten acts that talk about fame as much as Fall Out Boy does are rappers, although their take on selling records is less conflicted." Cory Apar of Allmusic opined that "Wentz' lyrics are oftentimes resentful, full of fame-induced angst, and really emphasize his need to drive home his position that stardom has not changed the band." The song discusses the band's
Best New Artist Grammy loss, and Wentz calls it the "most
narcissistic song on the album". The line "Fix me in forty-five" is a reference to the length of a therapy session. On "This Ain't a Scene, It's an Arms Race", Wentz uses wartime-inspired metaphors to discuss their newfound popularity; he called the song "kind of a tongue-in-cheek look at the way we are so addicted and obsessed with new arts, cultures and loves – to the point where it just becomes oversaturated." "I'm Like a Lawyer..." has been described as "about as close to a love song as you'll get from this band, a rare moment of tenderness among songs about blog entries, guest lists, and therapy sessions." In a tribute to the politicized Chicago
hardcore scene, Wentz describes the story of a rigged court case of African-American civil rights activist
Fred Hampton Jr. in "You're Crashing, But You're No Wave". The song has been described as a "very well-written track, a welcome respite from the one-liners which permeate the majority of the record." ==Packaging and title==