Name: MVSep MDX23 API: Music Stem Separation
Brand: magicapi
SKU: api-magicapi-music-demixing-api-lucataco-mvsep-mdx23-music-separation
Availability: InStock
Author: API Market

Shashank Agarwal

# 🎧 Music Stem Separation API: Vocals, Drums, Bass and Instrumental (lucataco MVSep MDX23)

## Overview
MVSep MDX23, packaged by lucataco, is the model built for the Music Demixing Track of the Sound Demixing Challenge 2023 (MDX'23). Send one song and the API splits it into separate stems: bass, drums, other, vocals and two instrumental versions.

The only input is `audio`. Each request returns six WAV file URLs.

## Features
- **Six stems per request**: `bass`, `drums`, `other`, `vocals`, `instrum` and `instrum2`.
- **Vocal and instrumental split**: get an isolated vocal track and instrumental versions of the same song.
- **One input**: send an audio file URL; there are no other settings.
- **WAV output**: each stem is returned as its own WAV file.

## Use Cases
1. **Karaoke and backing tracks**: take an instrumental stem to sing or play over.
2. **Remixing and sampling**: pull out drums, bass or vocals to rework them in a DAW.
3. **Practice tracks**: mute one part, such as bass or drums, by mixing the other stems.
4. **Audio analysis**: run transcription or pitch detection on the isolated vocal stem.

## Visual Examples
### Example Input
[Listen to the example input song](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-input-api-market.mp3)

### Example Output
The request returned six stems, in this order:
1. Bass: [Listen to the bass stem](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-1-j9g65160-api-market.mp3)
2. Drums: [Listen to the drums stem](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-2-j9g65160-api-market.mp3)
3. Other: [Listen to the other stem](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-3-j9g65160-api-market.mp3)
4. Vocals: [Listen to the vocals stem](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-4-j9g65160-api-market.mp3)
5. Instrumental (`instrum`): [Listen to the instrumental stem](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-5-j9g65160-api-market.mp3)
6. Instrumental 2 (`instrum2`): [Listen to the second instrumental stem](https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-6-j9g65160-api-market.mp3)

The live API returns WAV files; the examples above are MP3 copies for easy playback.

## Input Parameters
| Field | Type | Required | Default | Allowed values | Description |
| --- | --- | --- | --- | --- | --- |
| `audio` | string (URL) | Yes |  |  | Input audio file |

## Pricing
- **Pay As You Go (PAYG) pricing**: you only pay for what you use.
- **Price**: $0.39 per API unit.
- **1 API unit = 1 request with up to 360 seconds of processing.** A request that takes longer is billed one more unit for each started 360-second block (for example, 400 seconds of processing is 2 units, $0.78).
- Longer songs take longer to process and can add units.
- The example request took 85.3 seconds of processing, so it was billed 1 unit ($0.39).
- **Failed or cancelled predictions are not billed.**
- **GET requests to check prediction status** are free and don't count toward API unit usage.
- **No monthly subscription fee.**

## API Documentation

### Base URL
All API requests go to: `https://prod.api.market/api/v1/magicapi/music-demixing-api-lucataco-mvsep-mdx23-music-separation`

### Authentication
Send your api.market API key in the `x-api-market-key` header:
```
x-api-market-key: YOUR_API_MARKET_KEY
```

### Asynchronous Processing
**IMPORTANT**: This API is asynchronous. The flow is:
1. Send a POST request to `/predictions`. A successful request returns **201 Created** with a prediction `id` and a `status` of `starting` or `processing`.
2. Poll GET `/predictions/{id}` with that ID.
3. Keep polling while `status` is `starting` or `processing`.
4. Stop when `status` is `succeeded` (read `output`), `failed` or `canceled` (read `error`).

Separation can take several minutes. A polling interval of 2 seconds and an overall timeout of 900 seconds (15 minutes) work well.

### Endpoints

#### Create a Prediction
```bash
curl -X POST "https://prod.api.market/api/v1/magicapi/music-demixing-api-lucataco-mvsep-mdx23-music-separation/predictions" \
  -H "Content-Type: application/json" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY" \
  -d '{
    "version": "510b9b91aec1bfa7d634e6c06ee80c18492fb0fc06aa1474533fbda90dd3dba4",
    "input": {
      "audio": "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-input-api-market.mp3"
    }
  }'
```

Response (201 Created):
```json
{
  "id": "j9g65160qdrmy0d1d8k91yp668",
  "version": "510b9b91aec1bfa7d634e6c06ee80c18492fb0fc06aa1474533fbda90dd3dba4",
  "status": "starting",
  "created_at": "2026-10-23T19:04:47.192Z"
}
```

#### Check Prediction Status
```bash
curl -X GET "https://prod.api.market/api/v1/magicapi/music-demixing-api-lucataco-mvsep-mdx23-music-separation/predictions/{id}" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY"
```

Response when the prediction has finished (200 OK):
```json
{
  "id": "j9g65160qdrmy0d1d8k91yp668",
  "status": "succeeded",
  "output": [
    "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-1-j9g65160-api-market.mp3",
    "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-2-j9g65160-api-market.mp3",
    "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-3-j9g65160-api-market.mp3",
    "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-4-j9g65160-api-market.mp3",
    "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-5-j9g65160-api-market.mp3",
    "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-output-6-j9g65160-api-market.mp3"
  ],
  "error": null,
  "created_at": "2026-10-23T19:04:47.192Z",
  "started_at": "2026-10-23T19:04:48.192Z",
  "completed_at": "2026-10-23T19:08:47.192Z"
}
```

`output` is an array of six audio URLs in this order: bass, drums, other, vocals, instrum, instrum2. On the live API each file name ends with the stem name (for example `_vocals.wav`).

### Status Codes
- **201 Created**: prediction created (POST `/predictions`). This is the normal success response.
- **200 OK**: prediction details returned (GET `/predictions/{id}`).
- **400 Bad Request**: invalid input, for example a missing `audio`.
- **401 Unauthorized**: missing or invalid API key.
- **404 Not Found**: no prediction with that ID.
- **429 Too Many Requests**: rate limit exceeded.
- **500 Internal Server Error** or **503 Service Unavailable**: temporary server problem; retry later.

## Rate Limits
All plans allow 10 requests per second. Requests above that return `429 Too Many Requests`; back off before retrying and honour any `Retry-After` header. Polling a prediction with GET is free but still counts toward the per-second limit, so poll every 1 to 5 seconds rather than in a tight loop.

## Error Handling
- Check the HTTP status code of every request and read the response body for the error message.
- A prediction can also end with `status` set to `failed`; the `error` field then explains why (for example, an audio URL that cannot be downloaded). Failed predictions are not billed.
- Retry 429, 500 and 503 responses with exponential backoff. Fix the input before retrying a 400.

## Implementation Guide
### Example Code

#### JavaScript
```javascript
const apiKey = "YOUR_API_MARKET_KEY";
const baseUrl = "https://prod.api.market/api/v1/magicapi/music-demixing-api-lucataco-mvsep-mdx23-music-separation";

async function createAndWaitForPrediction(input) {
  const response = await fetch(`${baseUrl}/predictions`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-market-key": apiKey
    },
    body: JSON.stringify({ version: "510b9b91aec1bfa7d634e6c06ee80c18492fb0fc06aa1474533fbda90dd3dba4", input })
  });

  if (response.status !== 201) {
    throw new Error(`API error: ${response.status} ${await response.text()}`);
  }

  const prediction = await response.json();
  return pollForResults(prediction.id);
}

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

async function pollForResults(predictionId) {
  const maxTimeout = 900000;
  const pollInterval = 2000;
  const startTime = Date.now();

  while (Date.now() - startTime < maxTimeout) {
    const response = await fetch(`${baseUrl}/predictions/${predictionId}`, {
      headers: { "x-api-market-key": apiKey }
    });

    if (!response.ok) {
      throw new Error(`API error: ${response.status} ${await response.text()}`);
    }

    const prediction = await response.json();

    if (prediction.status === "succeeded") {
      return prediction.output;
    }

    if (prediction.status === "failed" || prediction.status === "canceled") {
      throw new Error(`Prediction ${prediction.status}: ${prediction.error || "Unknown error"}`);
    }

    await delay(pollInterval);
  }

  throw new Error("Prediction timed out after 15 minutes");
}

const stemNames = ["bass", "drums", "other", "vocals", "instrum", "instrum2"];

createAndWaitForPrediction({
  audio: "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-input-api-market.mp3"
}).then((output) => {
  output.forEach((url, index) => console.log(`${stemNames[index]}: ${url}`));
});
```

#### Python
```python
import time
import requests

API_KEY = "YOUR_API_MARKET_KEY"
BASE_URL = "https://prod.api.market/api/v1/magicapi/music-demixing-api-lucataco-mvsep-mdx23-music-separation"
STEM_NAMES = ["bass", "drums", "other", "vocals", "instrum", "instrum2"]


def create_and_wait_for_prediction(input_data):
    headers = {"Content-Type": "application/json", "x-api-market-key": API_KEY}
    response = requests.post(
        f"{BASE_URL}/predictions",
        headers=headers,
        json={"version": "510b9b91aec1bfa7d634e6c06ee80c18492fb0fc06aa1474533fbda90dd3dba4", "input": input_data},
    )

    if response.status_code != 201:
        raise Exception(f"API error: {response.status_code} {response.text}")

    return poll_for_results(response.json()["id"])


def poll_for_results(prediction_id):
    max_timeout = 900
    poll_interval = 2
    headers = {"x-api-market-key": API_KEY}
    start_time = time.time()

    while time.time() - start_time < max_timeout:
        response = requests.get(f"{BASE_URL}/predictions/{prediction_id}", headers=headers)

        if response.status_code != 200:
            raise Exception(f"API error: {response.status_code} {response.text}")

        prediction = response.json()

        if prediction["status"] == "succeeded":
            return prediction["output"]

        if prediction["status"] in ("failed", "canceled"):
            raise Exception(f"Prediction {prediction['status']}: {prediction.get('error') or 'Unknown error'}")

        time.sleep(poll_interval)

    raise Exception("Prediction timed out after 15 minutes")


output = create_and_wait_for_prediction({
    "audio": "https://blog.api.market/wp-content/uploads/2026/10/mvsep-mdx23-music-separation-input-api-market.mp3"
})
for name, url in zip(STEM_NAMES, output):
    print(f"{name}: {url}")
```

## FAQ
- **Which stems do I get?**
  - Six: bass, drums, other, vocals and two instrumental versions (`instrum` and `instrum2`), always in that order.
- **Can I ask for only the vocals?**
  - No. Every request returns all six stems; use the ones you need.
- **What audio formats can I send?**
  - Send a URL to a common audio file such as MP3 or WAV. The example uses an MP3.
- **How long does it take and what does it cost?**
  - Separation of a full song can take several minutes. Each request costs $0.39 per started 360 seconds of processing.
- **What if my prediction fails?**
  - Failed predictions are not billed. Read the `error` field, check that the audio URL is reachable and try again.

## Contact Us
If you have any questions, reach out to us through the chat on the bottom right of the page. You can also email our support team at hello@magicapi.com.


Separate any song into six stems with MVSep MDX23: bass, drums, other, vocals and two instrumental versions as WAV files. Pay as you go, no monthly fee.