What is an underscore in music?

An underscore is music written to sit beneath speech: dialogue in a film, a voiceover in a commercial, a presenter in a documentary, a speaker on a stage. It supports the emotional tone of the scene without competing for attention. Where a featured theme asks to be listened to, underscore asks to be felt, and the test of good underscore is that the audience remembers how the scene made them feel and could not hum what was playing. It is the workhorse of brand film: nearly every corporate video, explainer, launch film and documentary carries music under a voice, and the difference between amateur and professional work is audible in the first line.

Where it came from

The craft descends from Hollywood’s golden age. Max Steiner’s 1933 score for “King Kong” is widely credited with establishing continuous underscoring, music running beneath the drama and reacting to it moment by moment, and the approach shaped film and television for the rest of the century. Before Steiner, sound films mostly kept music to the titles and to scenes where someone was visibly playing it. After him, music under speech became the default language of screen storytelling, and audiences stopped noticing it, which was the point.

The craft of writing under a voice

• Stay out of the vocal register. The human voice lives in the middle of the spectrum. Melodies written there fight the words. Underscore keeps its lines above and below, and its busiest textures away from the moments of speech.
• Shape the dynamics to the lines. Amateur underscore is a loud track with the volume automated down whenever someone talks, which the ear hears as pumping. Professional underscore is written quieter under the lines and places its swells in the gaps, so nothing has to be turned down.
• Move with the meaning, not the words. Harmony changes on the ideas, a new section arrives on a change of subject, the resolve lands on the brand promise.
• Leave silence available. The most powerful tool in underscore is stopping. A line delivered over nothing, after two minutes of music, lands twice as hard.
• Write for the cut-downs. A brand film becomes a sixty, a thirty, a fifteen and a six. Underscore built in sections with clean edit points survives that. A through-composed piece does not.

Briefing underscore properly

Send the voice track. Composers who are given the voiceover, or the speech, or even a scratch read, write around it. Composers who are given the picture alone write music that will later be fought with. Say which lines matter most, where the film must lift and where it must hold back, and whether the music will also have to live without the voice, on social cuts or in an exhibition hall. Underscore is one of the quiet disciplines of long-form brand audio, and the brief is most of the discipline.

Underscore from our studio

When Masdar commissioned the music system for Abu Dhabi Sustainability Week 2026 and the Zayed Sustainability Prize ceremony, the brief was a deployable suite rather than a track, because event realities are unforgiving: speeches and voiceover need space, walk-ins need energy without overpowering, awards moments need lift without sounding theatrical. The music was built to work under people talking, which is underscore at its most exposed.

For New Murabba, Riyadh’s new downtown, we composed the original music and sound design for the brand film with Squint/Opera: a cinematic score that lifts through the panoramic reveal, leans warm on the human moments and resolves on the brand promise, built across an English and an Arabic cut with each language treated with the same care. For Emirates, when Dubai reopened to the world, the score had to carry the emotional weight of the moment without ever asking for attention: restrained where it needed to be, generous where it could be. And for STC’s Founding Day film, with Dejavu, the audio sits underneath the storytelling and lifts every frame without pulling focus from the visuals.

Underscore and the sonic identity

In a brand with a sonic identity, underscore is not generic. It is written from the brand’s sonic DNA, using the same palette and motifs as the sonic logo and the brand track, so that the music under a chief executive’s speech and the music under a product film are recognisably the same organisation. That is also what makes the logo land at the end: the melody has been underneath the whole film, quietly, and the sonic logo is simply the moment it surfaces.

Frequently asked questions

What is the difference between underscore and background music?
Background music fills a space and is not written to anything. Underscore is written to a specific piece of speech or action and changes with it.

Should underscore have a melody?
A light one, kept out of the vocal register and out of the moments of speech. Strong melodies belong in the gaps and the ending.

How loud should underscore be under a voiceover?
Quiet enough that every word is intelligible on a phone speaker, which is lower than most people mix it. The music is judged by whether the voice is clear, not by whether the music can be heard.

Can library music be used as underscore?
It can, and often is, which is why so many brand films sound the same. Library tracks are not written to the voice and rarely match the brand’s palette.

Related terms: voiceover, longform, stem, brand track, leitmotif. For the wider discipline, see sonic branding.