"Heard 'Em Say" is a midtempo hip-hop song that lasts for a duration of three minutes and twenty-three seconds. It harbors a soothing lullaby tone, with moody atmosphere and soulful undertones, containing a melodic R&B chorus as well as elements of art rock. The track has a subdued instrumentation which consists of piano chords, bass synth, and acoustic guitar while incorporating various bells, whistles and keyboards for its coda. Its musical composition is primarily built on cascading broken chords, with Adam Levine gently crooning over them in a luscious falsetto. The song contains excerpts of "Someone That I Used To Love" as performed by Natalie Cole. West employs an arpeggiated piano motif which forms a figure that runs throughout. According to the sheet music published at Musicnotes.com by Universal Music Publishing Group, the song is written in the time signature of common time, with a moderate tempo of 95 beats per minute. "Heard 'Em Say" is composed in the key of F major, while Levine's vocal range spans one octave and three notes, from a low of F4 to a high of B5. The song follows a basic sequence of F7–Bmaj7–F7–Bmaj7–Faug/G–F/A–F6/A–B/D–F6/A–B/D during the verses and coda and F7–Bmaj7–F7–Bmaj7–Faug/A at the chorus as its chord progression.