Chord Reharmonizer

A context-menu extension for Ableton Live 12 that reharmonizes the chord progressions you've already got — right in your clips, without hand-editing MIDI.

Right-click a MIDI clip → Reharmonize Section…, and a dialog reads the clip into chord blocks on a timeline. Select a section, then add a turnaround, chromatic approach chord, or passing chords — or place any chord in the key by hand — auditioning everything in context at your project tempo before you drop it in. Where Chord Progression Builder writes a new progression from scratch, Chord Reharmonizer transforms an existing one.

Features

• Reads your clip into chords. The extension analyzes the MIDI clip into chord blocks laid out on a bar/beat timeline, colored by a circle-of-fifths hue wheel so harmonically close chords get visually close colors.
• Opens in your key. It snapshots your Live Set's root + scale on open, so every suggestion is already in key. Override the key/mode at any time without losing your edits.
• Select any section — click a chord block (you hear its real notes) or drag across the timeline. Shift-click a block to just audition it without touching the selection. Edge handles and a draggable middle fine-tune the span, with a live rewriting N beats · from bar X readout.
• Context-aware reharmonization techniques — each reads the chord that follows your selection and offers musically correct options:
  • Turnarounds — cadential templates that lead back to the next chord (ii–V, I–vi–ii–V, iii–vi–ii–V, secondary-dominant, tritone-sub, and passing-diminished).
  • Approach — a chord placed right before the next one (tritone sub, half-step below, secondary dominant, leading-tone °7, parallel half-step).
  • Passing — a chord that bridges the preceding and following chords.
  • All chords — every diatonic and borrowed chord in the key; the ones that pull toward the next chord are ★ starred.
  • 🎲 Reimagine — rolls a progression that resolves into whatever follows the selection: chords are generated backward from the next chord (dominants, ii–Vs, tritone subs, leading-tone °7s, borrowed colors) and auto-played. Pick how many chords (auto / 1–6 — auto fits the selection length) and a vibe — subtle never leaves the key, classic adds secondary dominants and stock turnarounds, spicy raids the spice rack. 📌 Pin the cards you like and reroll: pinned chords survive untouched and rerolled ones keep their rhythm, so a roll converges instead of starting over.
• Audition before you commit. Suggestion chips play on a single click; a second click (or the + button) commits them. Tapping a timeline block, a rewrite card, or a palette chip plays it instantly.
• ▶ Listen plays the whole progression — your rewrite in context, original notes around it — tempo-synced with a sweeping playhead and a Loop toggle that picks up edits on the next pass. ▶ Section auditions just the rewrite and the chord it resolves into.
• Chord colors & voicings (CPB parity). Per-chord extensions (9ths, 13ths, sus, altered tensions) and voicings (Close, inversions, Open/drop-2, Drop-3, Wide, Rootless, Shell) — recomputed from the canonical chord so transforms never compound.
• Sits in the part. New chords are register-anchored to the original material's range instead of jumping to middle C. Optional Smooth voices voice-leads from the notes just before the selection, plus a Velocity slider and Humanize toggle.
• Multi-section editing. ✓ Lock in bakes the current section and frees the selection for the next one — reharmonize several spots in a single pass, with a 32-deep ↩ undo history.
• Write where you want. Apply into this clip (rewrites in place as one undo step, works for session and arrangement clips) or as a new clip ("<original> (reharm)" in the next empty session slot). Applying slices the original notes at the selection boundaries, so a chord ringing past the edge keeps its tail.

Screenshots

Your progression on a bar/beat timeline — click or drag to pick the section to reharmonize:

Context-aware technique tabs — each reads the chord that follows your selection:

Turnarounds	Approach
Passing chords	Every chord in the key (★ pulls to the next)

Per-card color, voicing, length & order	Audition: ▶ Listen / Loop / ▶ Section

✓ Lock in the current section to commit it and keep reharmonizing more spots in the same pass — then drop the whole rewrite into the source clip or a new one:

Requirements

• Ableton Live Suite 12.4.5 or newer (Extensions require Live Suite).

Install

1. Download Chord-Reharmonizer-1.0.0.ablx from the Releases page.
2. In Live, open Preferences → Extensions.
3. Drag the .ablx file into the Extensions list (or use the install button).
4. Right-click any MIDI clip and choose Reharmonize Section….

Note: Extensions are a Live Suite feature. The first time you install a community extension you may need to confirm the install in Live's dialog.

How to use

1. Right-click a MIDI clip → Reharmonize Section….
2. Select a section of the progression — click a chord block or drag across the timeline (shift-click a block to audition it without changing the selection).
3. Add a turnaround / approach / passing chord from the technique tabs, place chords by hand from the key palette, or hit 🎲 Reimagine (set the chord count + vibe next to the dice, 📌 pin keepers between rolls). Single-click a chip to hear it, click again (or +) to commit.
4. Shape each card's color, voicing, length, and order; toggle Smooth voices and Humanize; press ▶ Listen to audition at your project tempo.
5. (Optional) ✓ Lock in the section and move on to another spot in the clip.
6. Pick a destination and hit ✦ Drop it in — the rewrite lands in your clip.

Building from source

Requires Node ≥ 22.11.

npm install
npm run build       # type-check + production bundle
npm run package     # builds, then produces the distributable .ablx
npm run start       # build:dev + launch in Live (needs Live running + EXTENSION_HOST_PATH in .env)

How it works

The extension stays a thin reader/writer: it reads the clip + key once at open time and applies the final rewrite once. All analysis, editing, and rendering happen client-side in the dialog webview (which carries its own self-contained chord-detection and close-voicing engine — no tonal in the browser), with no round-trips in between.

• src/extension.ts — SDK activation, the tonal-based chord palette (diatonic + curated borrowed chords per mode), the clip/key snapshot, and writeReharmonizedClip (in-place / new-clip apply). Registers crh.open on the MidiClip context-menu scope.
• src/dialog.html — the entire UI and engine: clip→chord-block analysis, the timeline + selection state-machine, the ghost-preview renderer, the technique generators, register anchoring + auto voice-leading, the Web Audio instruments + loop transport, and the postMessage bridge.

Known limitations

• Assumes 4/4 — the SDK doesn't expose the clip's time signature, so the bar grid is fixed at 4 beats/bar.
• Chord-block detection is heuristic — tuned for root-position block chords; dense or arpeggiated clips may over-segment (the drag-select fallback covers those cases).
• Block-chord output — inserted chords are sustained blocks; they don't yet match the source clip's rhythm or per-chord velocity.
• "As a new clip" writes to a session slot — for arrangement clips, use the default in-place mode (which fully supports them).

Credits

Built by hello_nocap with the @ableton-extensions/sdk and the tonal music-theory library.

License

Released under the MIT License © 2026 hello_nocap.