Write a sound effect into a screenplay by putting it in an action line and capitalising the sound itself: a DOOR SLAMS behind her. Capitalise only the cue, not the whole sentence, and only for sounds that matter to the story. A script that capitalises every noise stops flagging anything at all.
Different formats treat cues differently, and an audio drama is stricter than a screenplay because sound is all it has.
How a sound cue looks in each format
| Format | Where the cue goes | Example |
|---|---|---|
| Screenplay | In an action line, sound capitalised | A door SLAMS in the hallway. |
| Audio drama | On its own cue line, numbered | SFX: Door slams, footsteps recede. |
| Stage play | In a stage direction | (A door slams offstage.) |
| Animation | In the action line, timed if critical | The anvil LANDS. Beat. Then a tiny DING. |
The convention for sound cues on the page
In a screenplay, a sound worth the reader's attention is written into the action lines and set in capital letters, for example: "A door SLAMS down the hall." The caps signal to the reader and the sound department that this is a deliberate audio moment, not incidental description. Keep the cue inside the flow of the scene rather than breaking it out on its own line, unless the sound itself is the event, such as a single unexpected GUNSHOT that lands as a beat.
Stage plays and radio scripts use a stricter form: the cue often sits on its own line, sometimes labeled as a sound effect or "SFX," because there is no camera to carry meaning and the sound is doing narrative work. Match the convention of the format you are writing in, and stay consistent from the first page to the last so a reader always knows a capitalized sound is a real cue.
When to specify a sound and when to hold back
Capitalize only the sounds that matter to the story or the reader's experience. A scene is full of ambient noise, but you do not write every footstep or passing car. Flag the sounds that carry meaning: the phone that RINGS at the worst moment, the floorboard that CREAKS and gives a hiding character away, the music that CUTS OUT before the bad news. If every sound is capitalized, none of them stand out, and the page starts to read like a cue sheet instead of a story.
Restraint also keeps you in your lane. A screenplay suggests the sound; it does not design it. Write "an alarm BLARES" rather than three lines specifying the frequency and decay, and let the sound team interpret. The exceptions are sounds that are plot-critical or tonally specific, where a short qualifier earns its place, for example "a soft, almost gentle CHIME" when the gentleness is the point.
Writing cues the sound team can build
A useful cue gives the sound team enough to work from without dictating the result. Four details do most of the work: the subject (what makes the sound), its texture (sharp, muffled, metallic, wet), the space it happens in (a tiled bathroom, an open field, a car interior), and its length or shape (a short snap, a long swelling rumble). Bake those into the line where you can, so "distant thunder" becomes "thunder ROLLS, low and far off," which reads better and briefs better at the same time.
- Subject: name the source clearly so there is no ambiguity about what is heard.
- Texture: one or two adjectives that fix the character of the sound.
- Space: where it happens, since a room changes a sound as much as the source does.
- Shape: how long it lasts and whether it hits, swells, or fades.
Turning a written cue into an actual sound on Morphic
The same details that make a good written cue make a good generation prompt, so your script does double duty. Take the line, for example "the door SLAMS in a tiled stairwell," and describe it to Morphic's sound effects tool as subject, texture, space, and length: a heavy door slam with a hard metallic edge, echoing in a tiled stairwell, short and sharp. Generate a few options, listen against the moment you pictured, and refine the wording if the space or weight is off. Because the tool creates original effects from text, you get the exact cue your script calls for rather than the nearest match in a stock folder, and one workspace also covers music and voiceover when a scene needs them. Browse the Morphic sound library for phrasing ideas, and once you have your files, place them in your editor the way you would for any edit, as covered in how to add sound effects to a video.
From the page to the actual cue
Three lines as they would appear in a script, and the sound each one is asking for.A door SLAMS
0:02The most-written cue in screenwriting. Weight and room are what the page cannot say.
Glass SHATTERS
0:02The page says shatters; the sound has to decide how much glass, and onto what.
Thunder ROLLS
0:07Distance is the whole choice here, and no script line ever specifies it.
To start from a finished cue instead of a blank prompt, the door slams, shattering glass and thunder pages each open in Studio with a working prompt already in the box.
FAQs
Yes. The convention is to put the sound in capital letters within the action line, such as a door that SLAMS, so the reader and the sound department recognize it as a deliberate cue rather than description.
No. Capitalize only the sounds that carry story or tone, like a phone RINGING at a key moment. Writing every ambient noise buries the cues that matter and turns the page into a cue sheet.
Stage plays and radio scripts often place the cue on its own line, sometimes labeled SFX, because there is no camera and the sound does narrative work. Match the convention of the format you are writing in.
Enough to brief the sound team without designing the effect for them: the subject, its texture, the space, and its length. Save extra detail for sounds that are plot-critical or tonally specific.
Yes. Feed the same details from your written cue into Morphic's sound effects tool, describing subject, texture, space, and length, and generate the effect from text so it matches the moment your script calls for.
Action lines. Dialogue is reserved for what characters say, and a cue placed there confuses the read. The exception is audio drama, where sound has its own numbered cue lines because there is no picture to carry the action.