Music montage

The music leads. Picture is cut to the song, never the other way round.

Workflow

1. Place the track first. Use the user's track; when none was supplied, choose one from stock (fetchStockMedia with mediaType:"audio" and audioPurpose:"music") or generate one where allowed (generateMedia kind music), because picking music is part of the edit. Ask only if the user said they would provide it.
2. Get measured beat timestamps before cutting (agentWorkspace action audio_inspect on the music clip). With no beat evidence, cut on the action and do not claim beat sync. Activate beat-sync for the grid mechanics.
3. Build a thread from the supplied media: the required people and moments, in order, each held long enough to read. Do not give every photo the same window.
4. Density follows the song. Sparse in verses (2 to 4 s a shot), dense on hits and drops (0.3 to 1 s). Save the best moment for the final hit and land the last cut on the last beat.
5. Slow motion is a speed ramp (one setKeyframeTrack with prop:"speed", 1.0 down to 0.3 to 0.5 into the peak and back), not a flat setSpeed, and only on the best moments. See speed-ramps.
6. One transition style, repeated on the beat, reads as intent (setTransitions); a different one on every cut reads as a template demo. Hard cuts are a valid style.
7. Grade for coherence. Correct shots individually, then one shared look on an adjustment layer that keeps skin natural (colour-grade).
8. Finish. Source audio that IS the song is not ducked. Fade music out at the end unless the last cut lands on the track's own ending. Titles and closing cards serve the occasion and are never automatic.

Gotchas