Sound and music
A motion piece is judged by ear as much as by eye. The plugin treats sound like picture: written in the storyboard, timed on picture events, measured, and with a licence for every file.
The four layers
- Voice carries the message; the mix aims at −16 to −14 LUFS, voice in front.
- Music gives energy and the cut rhythm; it ducks about 9 dB under the voice and ends on the end card (
umd mix --backtime). - Effects make events physical: an arrival, a click, a reveal. Two to five marked moments per 30 s, not one sound per move.
- Room tone is a very low air bed, so a pause never sounds like a dropout.
Listen to the palette
umd sfx <kind> makes these sounds with FFmpeg: nothing to download, no licence to track, the same file for the same settings. Vary --dur, --seed and --gain so a repeated sound does not read as stock.
umd sfx whoosh0.8 sa move across the frame, a transition; peak on the arrival frame
umd sfx swipe0.3 sa quick slide, a card flick, a UI swipe
umd sfx riser2 stension into a reveal; ends exactly on the hit frame
umd sfx impact1.2 sthe hero moment, a logo landing, a hard cut on a beat
umd sfx subdrop1.5 sweight under an impact or a scene change, felt more than heard
umd sfx click0.04 sa cursor press, a toggle, a key
umd sfx tick0.05 sa counter step, a clock, a list item appearing
umd sfx pop0.12 sa bubble, an icon or a badge appearing
umd sfx chime1 sa success state, a notification, a gentle end
umd sfx shimmer1.6 ssparkle on a premium reveal, light passing over glass
umd sfx glitch0.4 sa digital cut, an error, a tech transition
umd sfx roomtone5 sa quiet air bed under silence, so a pause never sounds like a dropout (raised 22 dB here so you can hear it)
Which sound on which event
| On screen | Sound | Timing |
|---|---|---|
| An element slides or enters | swipe or whoosh | Starts 2 to 4 frames before, peaks on the arrival |
| Build-up to a reveal | riser | Ends exactly on the reveal frame |
| Hero moment, logo landing | impact + subdrop | Attack 0 to 1 frame after the picture |
| Tail after the reveal | shimmer or chime | Starts with the impact, rings over the hold |
| Cursor press, toggle | click | On the press frame |
| Icon or badge appears | pop | On the first visible frame |
| Counter stepping | tick | One per step, up to 12 per second |
| Digital cut | glitch | Over the cut |
Each sound goes in the storyboard's ## Sound cues with its time; umd sync checks it lands within ±45 ms of its picture.
Find free sounds and music
umd sounds whoosh --cc0 --max 3umd sounds get <id>umd sounds ambient --music --limit 5umd sounds searches Freesound and Wikimedia Commons (effects) or Jamendo (music) through Openverse, keeping only CC0, CC BY and public domain. get downloads the file as 48 kHz WAV and records the author, licence and credit line in .motion/assets.lock.json. For CC BY music the credit line goes in the description or the end credits: umd licenses lists them.
For tailored music: ACE-Step 1.5 (MIT) locally, or a MIDI score written by Claude and rendered with FluidSynth. Never chart music, tracks ripped from video platforms, or a non-commercial licence.
By project type
| Project | Music | Effects |
|---|---|---|
| Promo, launch | Leads the edit, cuts on beats | Impacts on reveals, one riser into the hero moment |
| Presentation, explainer | A calm bed under the voice | Few: clicks, pops, ticks on step changes |
| Vertical short | A hook in the first half-second | Few and punchy; captions carry the message when muted |
| Logo animation | A 2 to 8 s sting | Riser, impact, a tail ringing over the held logo |
| Short film | Score with silences | Foley and ambiences per place |
| Web page | None by default | Short UI sounds, off until the user turns them on |
| 3D shot | Supports the material | Foley that matches the material: glass, metal, plastic |
The full guide, for the agent: references/audio/sound-design.md.