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

# Infill (Replace Section)

> Replace a section of a track with AI-generated content

## Endpoint

```http theme={null}
POST /api/v1/music/infill
```

**Asynchronous.** Returns a `task_id`. Poll [Get Task](/api-reference/tasks/get) for results.

Replaces a specified time range within an existing clip with new AI-generated content while keeping the rest of the track intact. Useful for fixing or improving a specific section.

## Request body

| Field            | Type    | Required | Description                                                                       |
| ---------------- | ------- | -------- | --------------------------------------------------------------------------------- |
| `clip_id`        | string  | **Yes**  | Clip ID of the source track.                                                      |
| `infill_start_s` | float   | **Yes**  | Start time (seconds) of the section to replace.                                   |
| `infill_end_s`   | float   | **Yes**  | End time (seconds) of the section to replace.                                     |
| `prompt`         | string  | No       | Description or lyrics for the replacement section. Supports Chinese and English.  |
| `tags`           | string  | No       | Style tags (e.g. `"摇滚 吉他"` or `"rock guitar"`).                                   |
| `mv`             | string  | No       | Model version override.                                                           |
| `callback_url`   | string  | No       | Webhook URL for completion notification. See [Webhooks](/api-reference/webhooks). |
| `retention_days` | integer | No       | Days to retain audio files. Default `7`.                                          |

## Response

```json theme={null}
{
  "code": 0,
  "message": "ok",
  "request_id": "req-1710000000000",
  "data": {
    "task_id": "64f3a1b2c8d9e0f1a2b3c4d5",
    "status": "queuing"
  }
}
```

## Example

```bash theme={null}
curl -X POST https://api.example.com/api/v1/music/infill \
  -H "Authorization: Bearer sk-mm-your-key" \
  -H "Content-Type: application/json" \
  -d '{
    "clip_id": "abc123def456",
    "infill_start_s": 45.0,
    "infill_end_s": 60.0,
    "prompt": "[桥段]\n电吉他独奏，充满力量",
    "tags": "摇滚 吉他独奏"
  }'
```