# Audio Calc – Interval Ratio Converter

> Audio Calc – Interval Ratio Converter is a paid API for AI agents from audio-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Converts a frequency ratio or cent value to cents, semitones, and octaves, names the just/Pythagorean interval, and optionally applies the interval to a base frequency in Hz.

## Facts

- Endpoint: GET https://audio-calc.x402tookit.com/interval-ratio?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/audio-calc-interval-ratio-converter-58df4e1a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vtp5M7V1zqFPUNf6S4UFX

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 audio-calc-interval-ratio-converter-58df4e1a
```

Example prompt: What is the 3:2 frequency ratio in cents and semitones, what just or Pythagorean interval is it named, and what Hz does it land on if I start from 440 Hz?

## When to prefer this

Choose this endpoint when you need precise musical interval arithmetic — converting between ratio, cents, and semitones representations — or when you need to identify whether an interval belongs to just intonation or Pythagorean tuning and quantify its deviation from equal temperament. Prefer it over general music theory lookups when you have a numeric ratio or cent value and need computation, not just a table lookup.

## Known failure modes

- Invalid or unparseable ratio string returns an error or null fields
- Providing both cents and ratio may cause ambiguity or only one to be used
- Very large ratios may fall outside named interval tables, returning null for intervalName
- Missing required input parameter returns a 400-level error
- baseHz of 0 or negative may produce undefined resultHz

## How this service works

Convert a frequency ratio (3:2) to cents and semitones or back, name just and Pythagorean intervals and commas, apply to Hz.

## Output

Returns a JSON object with the computed cents value, number of semitones, octaves, octave-reduced cents, deviation from equal temperament in cents, the recognized interval name (just or Pythagorean), nearest named ratio and interval with how many cents away, a simple fraction form, and optionally the resulting frequency in Hz when a base frequency is supplied.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "cents": {
       "type": "number",
       "description": "Interval size in cents (1200 per octave)"
      },
      "ratio": {
       "type": "string",
       "description": "Frequency ratio such as 3:2, 5/4 or 1.5 (use this, or cents)"
      },
      "baseHz": {
       "type": "number",
       "description": "Optional starting frequency in Hz to apply the interval to"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "cents": {
       "type": [
        "null",
        "number"
       ]
      },
      "ratio": {
       "type": [
        "null",
        "number"
       ]
      },
      "baseHz": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "octaves": {
       "type": [
        "null",
        "number"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "resultHz": {
       "type": [
        "null",
        "number"
       ]
      },
      "semitones": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "intervalName": {
       "type": [
        "null",
        "string"
       ]
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/audio-calc-interval-ratio-converter-58df4e1a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from audio-calc.x402tookit.com](https://www.zero.xyz/host/audio-calc.x402tookit.com/llms.txt)