# Music OpenVerbs Chord Builder

> Music OpenVerbs Chord Builder is a paid API for AI agents from music.openverbs.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Builds a chord from a root note and quality, returning note names, MIDI numbers, and semitone intervals spelled by stacked thirds.

## Facts

- Endpoint: POST https://music.openverbs.com/v1/chord
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/music-openverbs-chord-builder-65d44263
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_aL0YAdg0AkXr6oihgk1fu

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability music-openverbs-chord-builder-65d44263 -d '<json body>'
```

Example prompt: What notes, MIDI numbers, and intervals are in a C dominant 7th chord?

## When to prefer this

Choose this endpoint when you need programmatic, theory-correct chord spellings including MIDI note numbers and semitone intervals — especially for music apps, DAW automation, music education tools, or any agent needing structured chord data rather than a plain text description.

## Known failure modes

- Invalid root note format returns a validation error
- Unsupported chord quality not in the enum returns a 400 error
- Malformed request body missing required fields returns a schema validation error
- Payment not included or insufficient USDC causes a 402 payment required response

## How this service works

Build a chord from a root note and quality (major, minor, dim, aug, maj7, min7, dom7, dim7, half-dim7, sus2, sus4, maj6, min6). Notes are spelled by stacked thirds (C dom7 → C E G Bb). Returns the note names, MIDI numbers and semitone intervals.

## Output

Returns the chord's constituent note names (e.g. C, E, G, Bb), their corresponding MIDI numbers, and the semitone intervals between stacked thirds, all derived from the specified root note and chord quality.

## Request schema (JSON Schema)

```json
{
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "type": "object",
 "properties": {
  "input": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "type": "string",
     "enum": [
      "POST"
     ]
    },
    "bodyType": {
     "type": "string",
     "enum": [
      "json",
      "form-data",
      "text"
     ]
    },
    "body": {
     "type": "object",
     "properties": {
      "root": {
       "type": "string",
       "minLength": 1,
       "maxLength": 8,
       "description": "Root note, e.g. \"C4\"."
      },
      "quality": {
       "type": "string",
       "enum": [
        "major",
        "minor",
        "dim",
        "aug",
        "maj7",
        "min7",
        "dom7",
        "dim7",
        "half-dim7",
        "sus2",
        "sus4",
        "maj6",
        "min6"
       ],
       "description": "Chord quality."
      }
     },
     "required": [
      "root",
      "quality"
     ],
     "additionalProperties": false
    }
   },
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "additionalProperties": false
  }
 },
 "required": [
  "input"
 ]
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/music-openverbs-chord-builder-65d44263/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from music.openverbs.com](https://www.zero.xyz/host/music.openverbs.com/llms.txt)