background-music

Music bed

A talking video is often nearly done and still feels dry: no energy between the lines, dead air at the seams. A bed fixes that, as long as it stays under the voice. Drafting the brief costs nothing; the generation charges credits.

The brief

Draft it on the final picture. A bed scored on a cut that is still changing is scored twice.

Draft the brief from what the video already tells you, in two or three lines, so it can be read whole before anything is generated.

A brief names five things, and a model guesses whatever is missing:

Slot	From	Example
Genre	the transcript's tone, not its topic	warm lo-fi hip-hop
Instruments	the genre	mellow Rhodes, upright bass, soft vinyl crackle
Tempo and energy	the picture's pace	around 90 BPM, unhurried
Mood	what is said, and how	intimate and reflective
Purely instrumental, in positive words	always	purely instrumental throughout, carried by the instruments above

End it with what the bed is for: "sits quietly under a speaking voice without competing with it". references/prompt-craft.md has a brief for each kind of video and the mistakes that ruin one.

Instrumental under speech, always. Sung words fight the speech for the same ear, and both become mush. Say it in positive words: a music model can sing a bare negation, so "no vocals" or "no lyrics" may come back as a voice singing it. Write vocals in only when they were asked for; they will fight the dialogue.

Generate it

1. Pick a model from picsart_model_catalog with inputType: "music" and purpose: "generate", and read its fields with picsart_model_params. Use its instrumental switch when it has one, and leave any lyrics field empty: lyrics are what a voice sings, and a brief put there is sung.
2. Ask for a bed about a tenth longer than the video, rounded up to the second, within the model's own limit: music models tend to come back short. The mix trims a longer bed; a shorter one leaves silence at the end.
3. Validate the payload with picsart_preflight, whose estimate is the bed's price, then call picsart_generate once.

One generation per brief. A track that misses gets a new brief, with the steer applied to the slots it touches, and a new generation. Never fire variants hoping one lands.

Lay it under the speech

Run python3 scripts/music_bed.py bed.json on the final scene:

{
  "scene": "scene.json",
  "transcripts": {"talk": "transcript-talk.json"},
  "music": {"url": "<the bed's hosted URL>", "duration": 32.0}
}

transcripts names every spoken source's saved transcript by its asset id: a clip of the reel, a voice-over layer or a presenter's take alike, nested panels and bubbles included (the scene's own id for the source, not the nest's rec); footage-analysis says how a source gets one. duration is the bed's length, as the generation or picsart_media_probe reports it. The script adds the bed as one audio layer: faded in over 1 s and out over 2 s, at volume 30 between lines and 15 under speech, dipping just before each spoken stretch and coming back over 0.6 s after it. It prints the scene and the stretches it ducked under.

• The speech stays on top. When the bed competes, lower level and duck together; never raise the speech.
• No tool here reads a mix's loudness back, so nothing measures the bed against the voice; only a listener can. Move it by note: each note on how it sits moves level and duck together by about five points, and the script runs again on the same scene.
• Never drop the speech. Leave every clip's and voice-over's own sound as it is; the bed goes under it.

A different track is a new brief and a new generation, never a silent regeneration.

One video

The bed goes into the one video, never a music version beside a silent one. The licence caveat travels with it: a generated track's licence is the user's to check before a festival or a commercial use.

The bed never blocks the video. A generation that fails, or a bed that cannot be laid after one retry, leaves the scene as it was, without music.