Exporting Ableton Live Locators to JSON with Max for Live

When building music production tools and AI-powered analysis pipelines, one of the first challenges is getting structured data out of your DAW. Today, we'll walk through creating a Max for Live device that exports arrangement locators from Ableton Live to a clean JSON format.

This article documents a real proof-of-concept we built — a simple "EXPORT JSON" button that extracts:

• BPM (tempo)
• Locators/sections (INTRO, VERSE, CHORUS, etc.) with timestamps in seconds

The result is a portable JSON file that can feed into visualization tools, AI models, or cross-DAW workflows.

The Goal

We want a one-click solution inside Ableton Live that produces output like this:

{
  "project": "my_track",
  "bpm": 103.34,
  "sections": [
    { "label": "INTRO", "time_seconds": 0 },
    { "label": "VERSE", "time_seconds": 16 },
    { "label": "BRIDGE", "time_seconds": 80 },
    { "label": "CHORUS", "time_seconds": 112 },
    { "label": "OUTRO", "time_seconds": 224 }
  ]
}

This JSON can then be:

• Imported into other DAWs (REAPER, Logic, etc.)
• Used for automated video editing synced to song structure
• Fed into machine learning models for training
• Displayed in custom visualization tools

Prerequisites

To follow along, you'll need:

Architecture Overview

Our device consists of three components:

┌─────────────────┐     ┌──────────────────────┐     ┌────────────────┐
│   textbutton    │────▶│  js marker_export.js │────▶│   textedit     │
│  "EXPORT JSON"  │     │   (LiveAPI magic)    │     │  (JSON preview)│
└─────────────────┘     └──────────────────────┘     └────────────────┘

1. textbutton — The user clicks this to trigger export
2. js marker_export.js — JavaScript that queries Ableton's Live Object Model
3. textedit — Read-only display showing the exported JSON

Building the Max for Live Device

Step 1: Create the Patcher

Open Max for Live in Ableton (create a new Max MIDI Effect), then add these objects:

1. textbutton — Set the text to "EXPORT JSON"
2. js marker_export.js — This will hold our JavaScript logic
3. textedit — Enable "Read Only" in the Inspector

Step 2: Wire the Connections

This is where things get tricky. The textbutton object has three outlets:

Connect the third outlet of textbutton to the inlet of js marker_export.js, then connect the outlet of the JS object to textedit.

Step 3: Set Up Presentation Mode

For the device to be usable in Live's UI:

1. Select both textbutton and textedit
2. Open the Inspector (right sidebar)
3. Enable "Include in Presentation"
4. Switch to Presentation Mode (View → Presentation Mode)
5. Arrange the objects nicely

The JavaScript: marker_export.js

Here's the complete script that powers our device:

autowatch = 1;
outlets = 1;

function msg_int(v) {
  if (v === 1) bang();
}

function bang() {
  try {
    var song = new LiveAPI("live_set");

    // --- PROJECT NAME ---
    var name = song.get("name");
    name = Array.isArray(name) ? name[0] : name;
    if (!name || name === "") name = "untitled";
    name = name.replace(/[^a-z0-9_\-]/gi, "_");

    // --- BPM ---
    var bpm = song.get("tempo");
    bpm = Array.isArray(bpm) ? bpm[0] : bpm;

    // --- LOCATORS ---
    var locatorIds = song.get("cue_points");
    var sections = [];

    if (Array.isArray(locatorIds)) {
      for (var i = 0; i < locatorIds.length; i++) {
        if (typeof locatorIds[i] !== "number") continue;

        var l = new LiveAPI("id " + locatorIds[i]);
        var label = l.get("name");
        var time = l.get("time");

        sections.push({
          label: Array.isArray(label) ? label[0] : label,
          time_seconds: Array.isArray(time) ? time[0] : time
        });
      }
    }

    // --- BUILD JSON ---
    var data = {
      project: name,
      bpm: bpm,
      sections: sections
    };

    var json = JSON.stringify(data, null, 2);

    // Send to UI (textedit)
    outlet(0, "set", json);

    // Log to Max Console
    post("EXPORT SUCCESS\\n");

  } catch (e) {
    post("EXPORT ERROR:", e.toString(), "\\n");
  }
}

Key Concepts Explained

autowatch = 1 — Tells Max to reload the script automatically when the file changes. Essential during development.

LiveAPI — The bridge between JavaScript and Ableton's Live Object Model. We use it to access:

• live_set — The current project
• tempo — Current BPM
• cue_points — Array of locator IDs

Array handling — LiveAPI often returns single values wrapped in arrays, so we consistently check with Array.isArray().

outlet(0, "set", json) — The "set" message tells textedit to display the text without triggering its output.

Viewing the Output

The JSON output appears in the Max Console window:

Troubleshooting Common Issues

"js: can't find file marker_export.js"

Max can't locate your JavaScript file.

Solution:

1. Right-click on the js object in Max
2. Select "Open marker_export.js"
3. Save As... to the same folder as your .amxd file
4. Ensure the object text is just js marker_export.js (no paths)

"js: no function msg_int"

The button sends an integer, but your script doesn't have a handler for it.

Solution: Add this function to your script:

function msg_int(v) {
  if (v === 1) bang();
}

"Song object has no attribute 'locators'"

The LiveAPI path varies between Ableton versions.

Solution: Use cue_points instead:

var locatorIds = song.get("cue_points");

"SendMessage error 2: Bad parameter value"

Usually caused by:

• Invalid LiveAPI path
• Querying a property that doesn't exist
• Non-numeric values in the locator ID array

Solution: Filter IDs properly:

if (typeof locatorIds[i] !== "number") continue;

Adding File Export (Optional)

To save the JSON to disk, extend the script:

// --- FILE SAVE ---
var folder = "~/Documents/AbletonExports/";
var f = new File(folder + name + ".json", "write");

if (f.isopen) {
  f.writestring(json);
  f.close();
  post("Saved to:", folder + name + ".json", "\\n");
} else {
  post("EXPORT ERROR: cannot write file\\n");
}

Note: The ~ path expansion can be inconsistent in Max/JS. For reliability, either:

• Use absolute paths
• Save to the project folder
• Create the target directory manually first

Packaging for Distribution

The Simple Way (Recommended for MVP)

Create a folder with both files:

MTL_LocatorsToJSON/
├── MTL_LocatorsToJSON.amxd
├── marker_export.js
└── README.txt

Compress to ZIP and share. Recipients should:

1. Unzip the folder
2. Copy to: ~/Music/Ableton/User Library/Presets/MIDI Effects/Max MIDI Effect/
3. Restart Ableton Live (or refresh the Browser)

Why Not .alp (Ableton Pack)?

The .alp format is not a simple ZIP with a different extension. Creating valid Packs requires Ableton's specific export workflow, which varies between Live versions. For quick distribution, a ZIP folder is more reliable.

Project Folder Structure

Usage Instructions

1. Add the device to any MIDI track
2. Create locators in the Arrangement view (right-click → Add Locator, or Ctrl/Cmd+Shift+L)
3. Name your locators (INTRO, VERSE, CHORUS, etc.)
4. Click EXPORT JSON
5. Copy the JSON from the text display or find it in your export folder

Integration with AI Workflows

This JSON format is designed to be compatible with our song structure analysis pipeline. You can:

1. Export manually-annotated structures from Ableton
2. Compare with AI-detected structures
3. Train custom models on your annotations
4. Import AI-generated structures back into your DAW

What's Next?

This MVP opens several possibilities:

Complete Code Reference

The final working script:

autowatch = 1;
outlets = 1;

function msg_int(v) {
  if (v === 1) bang();
}

function bang() {
  try {
    var song = new LiveAPI("live_set");

    // PROJECT NAME
    var name = song.get("name");
    name = Array.isArray(name) ? name[0] : name;
    if (!name || name === "") name = "untitled";
    name = name.replace(/[^a-z0-9_\-]/gi, "_");

    // BPM
    var bpm = song.get("tempo");
    bpm = Array.isArray(bpm) ? bpm[0] : bpm;

    // LOCATORS
    var locatorIds = song.get("cue_points");
    var sections = [];

    if (Array.isArray(locatorIds)) {
      for (var i = 0; i < locatorIds.length; i++) {
        if (typeof locatorIds[i] !== "number") continue;

        var l = new LiveAPI("id " + locatorIds[i]);
        var label = l.get("name");
        var time = l.get("time");

        sections.push({
          label: Array.isArray(label) ? label[0] : label,
          time_seconds: Array.isArray(time) ? time[0] : time
        });
      }
    }

    // JSON OUTPUT
    var data = {
      project: name,
      bpm: bpm,
      sections: sections
    };

    var json = JSON.stringify(data, null, 2);
    outlet(0, "set", json);

    // OPTIONAL: File save
    var folder = "~/Documents/AbletonExports/";
    var f = new File(folder + name + ".json", "write");
    if (f.isopen) {
      f.writestring(json);
      f.close();
    }

  } catch (e) {
    post("EXPORT ERROR:", e.toString(), "\\n");
  }
}

Conclusion

With about 50 lines of JavaScript and a simple Max for Live patcher, we've built a bridge between Ableton Live's arrangement markers and the wider world of data-driven music tools.

This approach demonstrates a key principle: start with the simplest thing that works. A button, a script, and a text display. No complex UI, no elaborate state management. Just structured data flowing from your DAW to wherever it needs to go.

The JSON format we've chosen is intentionally minimal — project name, BPM, and an array of labeled timestamps. This makes it trivial to parse in any language and integrate with any system.

At Music Tech Lab, we build tools at the intersection of music production and software engineering. Have a Max for Live challenge or want to discuss DAW integration strategies? Get in touch.