/beat-sync-montage

name: beat-sync-montage
description: |
  Plan and build a finished beat-synced montage where cut placement serves the content, not just the metronome.
  Use for 卡点混剪, 卡点剪辑, 踩点视频, beat-sync montage, rhythm edit, 节奏剪辑, 音乐驱动剪辑, or when the user wants cuts that land on the beat.

Beat Sync Montage

Use this workflow when the edit should be driven by music. The failure mode to avoid is a metronome edit: every cut technically lands on a beat, and the result still feels mechanical, tiring, or unrelated to what is on screen.

This workflow decides **what** to cut and **why**. It does not re-explain the music tools — when you reach an execution step, follow `music-intelligence` for `analyze_music`, `music_edit_plan`, and `sync_cuts_to_music`. Load it there.

This is a OpenChatCut-native workflow. Use the current project, source assets, asset-frame inspection, AV/script context, and OpenChatCut editing tools.

When to switch workflows

• Beat-synced photos on a locked, empty track → `music-intelligence` handles this directly with `music_image_plan`. This workflow is for video montage.
• One long source cut to speech rhythm → `long-video-to-shorts`.
• Many clips packaged as highlights without music driving the cut → `multi-clips-to-reels`.
• N distinct beat-synced variants from one pool → `batch-montage-variants`, using this workflow for each cut.

Workflow

1. Confirm the track is on the timeline and identified. Read the music first: BPM, meter, sections, and energy shape. Use `music-intelligence` → `analyze_music` or `inspect_music`; never request the CLAP embedding. 2. Judge whether the material actually suits a beat edit. See [references/shot-fitness.md](references/shot-fitness.md). Footage with no clear motion onset, or whose motion contradicts the music's energy, will not improve by cutting on every beat. Say so instead of forcing it. 3. Choose the **density arc** before choosing individual cut points. See [references/beat-density.md](references/beat-density.md). Density is a property of the whole piece, not a per-cut decision: a verse and a chorus should not be cut the same way. 4. Assign content to the music's structure. Map sections to narrative roles — intro to the hook, verse to context, build to escalation, drop/chorus to payoff. Cut density follows that map. 5. Pick the anchor points first: 3–6 moments where a cut must hit a downbeat or a section boundary because the content has real impact there. See [references/beat-density.md](references/beat-density.md). Everything else is filler rhythm between anchors. 6. Fill between anchors at the density chosen for that section. Do not fill uniformly — uniform filling is what makes an edit feel mechanical. 7. Reserve breathing room. See [references/beat-density.md](references/beat-density.md). A montage that never stops cutting exhausts the viewer and hides the anchors you built in step 5. 8. Check motion continuity across cuts. See [references/shot-fitness.md](references/shot-fitness.md). Consecutive cuts should not fight each other in screen direction or motion axis unless the collision is deliberate. 9. Plan with `music_edit_plan`, show the bounded summary and any cap warning, and get acceptance. Then apply with `sync_cuts_to_music` and the returned `analysisRef`. Follow `music-intelligence` for both. 10. QA by watching, not by counting. See the rules below. A cut list that is 100% on-beat can still be a bad edit.

Plan Format

• Track, BPM, meter, section map with timecodes
• Density arc per section (sparse / medium / dense / rest)
• Anchor points: frame, musical event, and what lands there
• Shot order with the reason each shot sits where it does
• Breathing points: where the edit deliberately stops cutting
• Risks: weak motion onsets, motion-direction collisions, sections that outrun the material

Rules

• **Anchors over uniformity.** Three or four meaningful downbeat hits beat forty evenly spaced ones.
• **Density follows the music, not the maximum.** Dense cutting is a choice for a section, not a default for the piece.
• **Never cut a strong shot short to satisfy a beat.** If a moment needs four beats, give it four beats and adjust around it.
• **Protect the hook.** The first downbeat hit should land within the first three seconds. A beat edit that eases in has wasted its advantage.
• **Breathe.** At least one held shot per 15 seconds unless the brief explicitly asks for relentless pace.
• **Motion must be legible.** A cut that lands on a beat but lands mid-action with no visible onset reads as an error, not as rhythm.
• **The cut serves the content.** If a section has nothing worth cutting, hold the shot and let the music carry it.
• Do not use captions to invent claims the footage does not support.
• Report honestly when the material does not support the requested density.