> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apimart.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Extend Music

> Flow Music continues a previously generated audio clip. Extends the music from a specified time point according to an editing instruction

<RequestExample>
  ```bash cURL theme={null}
  curl --request POST \
    --url https://api.apimart.ai/v1/music/generations/extendFlowMusic \
    --header 'Authorization: Bearer <token>' \
    --header 'Content-Type: application/json' \
    --data '{
      "model": "flowmusic",
      "clip_id": "abc123-def456",
      "extend_from_s": 30,
      "extend_s": 60,
      "instruction": "Continue the verse melody, add strings"
    }'
  ```

  ```python Python theme={null}
  import requests

  url = "https://api.apimart.ai/v1/music/generations/extendFlowMusic"

  payload = {
      "model": "flowmusic",
      "clip_id": "abc123-def456",
      "extend_from_s": 30,
      "extend_s": 60,
      "instruction": "Continue the verse melody, add strings"
  }

  headers = {
      "Authorization": "Bearer <token>",
      "Content-Type": "application/json"
  }

  response = requests.post(url, json=payload, headers=headers)

  print(response.json())
  ```

  ```javascript JavaScript theme={null}
  const url = "https://api.apimart.ai/v1/music/generations/extendFlowMusic";

  const payload = {
    model: "flowmusic",
    clip_id: "abc123-def456",
    extend_from_s: 30,
    extend_s: 60,
    instruction: "Continue the verse melody, add strings"
  };

  const headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
  };

  fetch(url, {
    method: "POST",
    headers: headers,
    body: JSON.stringify(payload)
  })
    .then(response => response.json())
    .then(data => console.log(data))
    .catch(error => console.error('Error:', error));
  ```
</RequestExample>

<ResponseExample>
  ```json 200 theme={null}
  {
    "code": 200,
    "data": [
      {
        "status": "submitted",
        "task_id": "task_01KWXVCYB70YJ1WY9X22RVYRNP"
      }
    ]
  }
  ```

  ```json 400 theme={null}
  {
    "error": {
      "message": "clip_id is required",
      "type": "invalid_request",
      "param": "",
      "code": "invalid_request"
    }
  }
  ```

  ```json 403 theme={null}
  {
    "error": {
      "message": "Insufficient balance",
      "type": "invalid_request",
      "param": "",
      "code": "quota_not_enough"
    }
  }
  ```

  ```json 429 theme={null}
  {
    "error": {
      "message": "Current group capacity is saturated, please retry later",
      "type": "rate_limit_error",
      "param": "",
      "code": "rate_limit_error"
    }
  }
  ```
</ResponseExample>

## Authentication

<ParamField header="Authorization" type="string" required>
  All endpoints require Bearer Token authentication

  Get your API Key:

  Visit the [API Key management page](https://apimart.ai/keys) to get your API Key

  Add it to the request header:

  ```
  Authorization: Bearer YOUR_API_KEY
  ```
</ParamField>

## Request Parameters

<ParamField body="model" type="string" required>
  Model name, **must be `"flowmusic"`** (case-insensitive)
</ParamField>

<ParamField body="clip_id" type="string" required>
  Source music clip\_id, from a successful task's `result.music[].clip_id`

  <Note>
    The source task must have succeeded. External audio can first be imported via [Upload Audio](./upload-audio) to obtain a clip\_id.
  </Note>
</ParamField>

<ParamField body="extend_from_s" type="number" required>
  Time point (seconds) to start the extension from

  Cannot exceed the source clip's duration
</ParamField>

<ParamField body="extend_s" type="number" required>
  Extension duration (seconds)

  Maximum: `164` seconds
</ParamField>

<ParamField body="instruction" type="string" required>
  Editing instruction for the extended music

  Example: `"Continue the verse melody, add strings"`
</ParamField>

<ParamField body="title" type="string">
  Title of the extended music
</ParamField>

<ParamField body="seed" type="string">
  Random seed, used to reproduce results
</ParamField>

## Response

<ResponseField name="code" type="integer">
  Response status code, 200 on success
</ResponseField>

<ResponseField name="data" type="array">
  Array of returned data

  <Expandable title="Array elements">
    <ResponseField name="status" type="string">
      Task status, `submitted` upon initial submission
    </ResponseField>

    <ResponseField name="task_id" type="string">
      Unique task identifier, used to query task status and results
    </ResponseField>
  </Expandable>
</ResponseField>

## Use Cases

### Scenario 1: Extend 60 seconds from the chorus

```json theme={null}
{
  "model": "flowmusic",
  "clip_id": "abc123-def456",
  "extend_from_s": 30,
  "extend_s": 60,
  "instruction": "Continue the verse melody, add strings"
}
```

<Note>
  **Query Task Results**

  Music extension is an asynchronous task; a `task_id` is returned after submission. Use the [Get Task Status](./query) endpoint to query generation progress and results. The extension output is a **new** `clip_id`; use the new clip\_id for subsequent operations.
</Note>

## Completed Task Result Example

**Query response example** (`GET /v1/music/tasks/{task_id}`):

```json theme={null}
{
  "code": 200,
  "data": {
    "id": "task_01KWXVCYB70YJ1WY9X22RVYRNP",
    "status": "completed",
    "progress": 100,
    "created": 1783413242,
    "completed": 1783413292,
    "actual_time": 50,
    "cost": 0.048,
    "credits_cost": 0.48,
    "result": {
      "music": [
        {
          "clip_id": "d2f589ea-5390-4e83-8e2f-4517420408fa",
          "title": "Untitled (Extended)",
          "duration_seconds": "39.95733333",
          "create_time": "2026-07-07T08:34:33.240020Z",
          "lyrics": "waking up to the morning light,\n...",
          "lyrics_id": "0452451b-9e54-5d9f-8437-8bff97c7bbc8",
          "lyrics_timing_markers": [[0, 12], [129, 20]],
          "audio_url": "https://cdn.apimart.ai/audio/flowmusic_d2f589ea.m4a",
          "wav_url": "https://cdn.apimart.ai/audio/flowmusic_d2f589ea.wav",
          "image_url": "https://cdn.apimart.ai/image/flowmusic_d2f589ea_cover.jpg"
        }
      ]
    }
  }
}
```