feat: AI arrangement assistant — intelligent next-section and orchestration suggestions

[ChuxiJ]

Context

From DAW tech stack research: Suno Studio is positioning as an "AI-native DAW" but lacks real DAW functionality. We already have 4 AI models (Text2Music, Lego, Cover, Repaint) and a sophisticated generation pipeline. The next step is moving beyond "generate a clip" to intelligent arrangement assistance.

No traditional DAW (Ableton, Bitwig, FL Studio) offers this. Suno/Udio generate full songs but can't help you arrange them. This is a blue-ocean opportunity.

Goal

Build an AI arrangement assistant that understands musical structure and helps users compose complete songs, not just individual clips.

Acceptance Criteria

• Analyze current arrangement: detect sections (intro, verse, chorus, bridge, outro)
• Suggest next section based on genre conventions and current arrangement
• Recommend instrumentation/orchestration changes between sections
• Chord progression suggestions that fit the current harmonic context
• "Fill gap" — auto-suggest content for empty regions in the timeline
• One-click accept/reject for each suggestion
• Suggestions respect existing tempo, key, and time signature

Strategic Context

Competitive gap: No DAW offers this — Ableton has no AI, Suno has no arrangement view
Our advantage: LEGO pipeline + context-aware generation + full arrangement store
Builds on: generationStore, generationPipeline, projectStore

Part of: DAW Best Practices Research Series

[ChuxiJ]

Priority Update: P1 → P3

Strategic new capability. Deferred until core experience polish (P0/P1) is complete. Re-prioritized as part of Experience Polish Series.

---

Generated by Claude Code