Solo acoustic guitar states the chord loop before any voice; a soft ooh at 0:04 leads into Bruno Mars entering low and conversational around 0:10. Bass joins near 0:28 as the verse narrows into its first pre-chorus at 0:30. Everything here is introduction: the loop, the lone lead voice, the slow addition of support.

Drums slip in just before 0:40, and the chorus at 0:45 opens the arrangement out for the first time — If the world was ending. This single full run establishes the song's contract: quiet verse, broad duet-ready chorus. It states the refrain once, then is cut off.

The chorus ends on a lingering chord, and for roughly fifteen seconds the track returns to near its opening state — solo guitar, then soft pads. Lady Gaga takes the second verse at 1:26, lost in the words that we scream, with Mars joining in harmony at 1:38, so the second pass arrives with a changed lead voice. Drums re-enter around 1:45 as the pre-chorus rebuilds as a duet.

The same refrain returns redistributed across both voices, the fullest singing yet, and runs longer than its first statement, extending to Right next to you at 2:38.

At 2:40 the rhythm pauses under a sustained vocal; drums, then bass, then the voices themselves drop away by 2:54, leaving the opening guitar alone again. This is the delay before the last chorus — the song stripped to its first material.

The last If the world was ending re-enters hushed around 3:10; drums return softly near 3:31 and the duet gathers to its largest statement, landing die with a smile at 3:38. The closing wish at 3:50 and a final ooh ease off before the last chord rings from about 4:03 and decays alone.

One loop, run three times with an expanding cast, then returned to its opening guitar — so the final chorus lands as arrival rather than repeat.