The common mistake is to write a song and then turn it down. Underscore is a different thing built for a different job. It holds a mood under a scene and does its best work when nobody in the audience notices it is there, and that changes how you write every bar of it.
For anyone scoring picture: film, short, documentary, trailer, game cutscene.
Underscore is music written to support a scene without pulling focus from it. It sits under dialogue and action, colours how a moment feels, and succeeds when the audience feels the scene more strongly without consciously hearing the music at all.
That is the whole difference from a song. A song is built to be listened to. It has a hook, a structure it controls, a beginning and an end on its own terms, and often words that ask for your full attention. Underscore gives all of that away. It does not need to be memorable on its own, it does not get to resolve when it wants to, and it never competes with the thing on screen. The picture is the subject. The music is there to serve it.
If a viewer walks out of a quiet dialogue scene humming the tune, the music was probably doing too much. There are moments built to be noticed, a main theme over a landscape or the cue on the end credits, but those are the exception. The default job of underscore is to stay under the threshold of attention.
You reduce it to one idea and let that idea move slowly. Almost everything else follows from those two decisions. Here is what they mean in practice.
A single line, or a single texture, is usually enough. Every extra part is one more thing the ear has to track, and tracking is attention. Strip the cue back until taking away one more element would break it, then stop there.
Hold a chord where a song would change three or four times. Slow harmonic drift reads as mood. Fast changes read as events, and an event pulls the ear back onto the music and off the scene. A cue can live on two chords for a minute and be all the better for it.
Write below and above speech. Low pads and drones underneath, air and shimmer on top, and keep the band between roughly 1 kHz and 4 kHz clear, because that is where the consonants that carry meaning in a voice live. Music with nothing in the middle sits under dialogue at a healthy level and never fights it. The frequency side of this is covered in how to mix music under dialogue.
A strong beat competes with the rhythm of the cut and the rhythm of the lines. An ambiguous pulse, a slow one, or none at all, stays out of the way. Save the driving rhythm for the moment the scene has no dialogue to protect.
Write to the cut, not the other way round. The scene sets the pace, and the music follows the shot and the line. Do not make an actor wait for your phrase to finish resolving, and do not ask the editor to hold a cut so your bar can land. When the two disagree, the picture wins.
A strong melody with a clear arc becomes the thing the audience follows, which is the opposite of what you want under a scene. A repeated cell, a held note, or a short motif does the emotional work without asking to be listened to. This is the real split from songwriting: a song resolves on its own terms, and underscore resolves on the picture's.
You change one thing at a time, slowly, and you hold the release until the picture asks for it. Tension under a scene is built from small gradual moves, not big gestures. A gesture is an event, and an event pulls focus. A slow change is felt without being noticed, which is exactly the line you are trying to stay on.
Ways to raise tension quietly:
The release lands on a picture cue, not on the music's own schedule. Resolve the harmony, arrive on a full chord, or drop out entirely at the cut, the reveal, or the line the scene turns on. Resolve early and the scene goes slack under you. Let the music peak before the picture does and you have pulled focus onto the score, which is the one thing underscore is meant not to do.
Tension also lives in the dynamics across a whole scene. Music sits low and out of the way under the dialogue, then comes up, or takes over completely, on the wide shot with no words. Moving between those two states is a great deal of what makes a scene feel scored rather than soundtracked. How far under the dialogue the music should sit while it is low, and how to keep it there without it fighting the words, is its own craft, written up in how to mix music under dialogue.
You put it in a believable acoustic space, so it reads as part of the world instead of laid flat on top of it. Film music comes in two kinds. Score sits outside the world of the film and only the audience hears it. Source music, or diegetic music, exists inside the scene: a radio on the counter, a band down the hall, a car stereo. Most underscore is score, but the line between the two is where a lot of the useful craft lives.
Even pure score sits better with a sense of space. A dry pad pasted over the image tends to sound like it is sitting on the glass in front of the picture. The same pad with a real sense of room, distance and reflection sounds like it belongs to the shot rather than to the studio it was recorded in.
When the music is meant to come from inside the scene, placing it is the whole job. Music heard from the next room, down the hall, or out in the street is shaped by the walls, the distance and the doorway between it and the camera. Get that right and it stops sounding like a track laid over picture and starts sounding like a location. The filtering that does this, and the mistakes that make it sound fake, are in how to make music sound like it is playing in another room.
There is a bonus in this for dialogue. A wall between the music and the microphone removes the midrange for you, the same midrange that speech needs kept clear. So a source cue that is properly placed will often stop fighting the words on its own, before you touch a fader.
THALM places music in a real acoustic space for film: the next room, down the hall, out in the street. You set a place on a cutaway of a building rather than dialling filters, and the walls, distance and doorway do the work. That is exactly how you make an underscore feel diegetic, or tuck a cue behind a scene so it sits under the dialogue on its own.
It follows your playhead, so the placement moves with the shot instead of being keyframed by hand. Hear the whole thing free in your browser first, no install and no account. If you want the technique rather than the plugin, the manual method is written up in how to make music sound like it is playing in another room, free.
We write these when there is something worth writing down. One email when a new one lands or a new Tunary instrument ships. No newsletter, no schedule.
Tunary