POST
/
extend
Python
import requests

url = "https://api.musicgpt.com/api/public/v1/extend"
headers = {"Authorization": "<API_KEY>"}
data = {
  "extend_after": 35.0,
  "prompt": "Add a calming piano outro",
  "lyrics": "Let the journey fade away",
  "gender": "neutral",
  "webhook_url": "https://example.com/webhook"
}

# Option 1: audio_url
data["audio_url"] = "https://mybucket.s3.amazonaws.com/song.mp3"
response = requests.post(url, headers=headers, data=data)

# Option 2: File Upload
# with open("song.mp3", "rb") as f:
#     files = {"audio_file": f}
#     response = requests.post(url, headers=headers, data=data, files=files)

# print(response.json())
{
  "success": true,
  "message": "Extend request submitted successfully",
  "task_id": "task-extend-789",
  "conversion_id_1": "extend-a1b2",
  "conversion_id_2": "extend-c3d4",
  "eta": 38,
  "credit_estimate": 42
}
Extend an existing audio file by generating new content after a specific timestamp.

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Endpoint

POST /extend
This endpoint allows users to extend an existing audio file or stream by appending new audio content after a specific timestamp. The new content is generated using a prompt and optional lyrics.

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Request Parameters

ParameterTypeRequiredDescription
audio_fileUploadFileOptionalUpload the audio file to extend. Required if audio_url is not provided.
audio_urlStringOptionalPublic or S3 URL to the input audio. Required if audio_file is not provided.
extend_afterFloatRequiredTime (in seconds) after which new audio is generated.
promptStringOptionalDescribes the desired extension sound. Example: “Add a melodic flute section”
lyricsStringOptionalOptional lyrics for the extended segment. Max 2000 characters.
genderStringOptionalVoice style if vocals are generated. Must be one of male, female, neutral.
webhook_urlStringOptionalCallback URL for async result delivery.
💡 Note: You must provide either audio_file or audio_url — at least one is required.

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Sample Output

Listen to a sample output: Prompt: Add a calming piano outro. Download Audio

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Try it Yourself

Visit the Extend Endpoint Explorer to play around — set your payload, hit send, and listen to the generated results live.

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Sample Request

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cURL

curl -X POST "https://api.musicgpt.com/api/public/v1/extend" \
-H "accept: application/json" \
-H "Authorization: <api_key>" \
-F "audio_file=@/path/to/audio.mp3" \
-F "extend_after=35.0" \
-F "prompt=Add a calming piano outro" \
-F "lyrics=Let the journey fade away" \
-F "gender=neutral" \
-F "webhook_url=https://example.com/webhook"

​
Python

import requests

url = "https://api.musicgpt.com/api/public/v1/extend"
headers = {"Authorization": "<API_KEY>"}
data = {
  "prompt": "Add a calming piano outro",
  "lyrics": "Let the journey fade away",
  "extend_after": 35.0,
  "gender": "neutral",
  "webhook_url": "https://example.com/webhook"
}

# Option 1: audio_url
files = {}
data["audio_url"] = "https://lalals.s3.amazonaws.com/audio/example.mp3"
response = requests.post(url, headers=headers, data=data, files=files)

# Option 2: File Upload
# with open("audio.mp3", "rb") as f:
#     files = {"audio_file": f}
#     response = requests.post(url, headers=headers, data=data, files=files)

# print(response.json())
🔐 Replace {path_to_your_audio_file}, api_key, and webhook_url before executing.

​
Sample Response

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Success (200 OK)

{
  "success": true,
  "message": "Extend request submitted successfully",
  "task_id": "task-extend-789",
  "conversion_id_1": "extend-a1b2",
  "conversion_id_2": "extend-c3d4",
  "eta": 38,
  "credit_estimate": 42
}

​
Webhook Response

When the extension process completes, the webhook receives: 
{
  "success": true,
  "conversion_type": "Extend",
  "task_id": "task-extend-789",
  "conversion_id": "extend-a1b2",
  "conversion_path": "https://lalals.s3.amazonaws.com/conversions/extend-a1b2.mp3",
  "conversion_path_wav": "https://lalals.s3.amazonaws.com/conversions/extend-a1b2.wav",
  "conversion_duration": 192.12,
  "is_flagged": false,
  "reason": "",
  "lyrics": "Let the journey fade away",
  "lyrics_timestamped": [],
  "title": "Outro Symphony"
}

​
Webhook Delivery

Once the generation is complete, webhooks will be triggered to deliver the following:

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Standard Requests (non-instrumental):

  • 2 (webhooks) x Extend conversion details (one per version)
  • 2 (webhooks) x Lyrics with timestamp data
Webhook responses include detailed metadata including task_id, conversion_id, audio files (conversion_path), lyrics etc.

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Common Errors

  • 422 Unprocessable Entity: Missing required fields like extend_after, or neither audio_file nor audio_url provided.
  • 500 Internal Server Error: An unexpected error occurred during processing.
The response provides a downloadable or streamable extended audio file.

Authorizations

​
Authorization
string
header
required

Body

multipart/form-data
​
audio_url
string
required

URL or S3 path to the input audio.

Example:

"https://mybucket.s3.amazonaws.com/song.mp3"

​
extend_after
number
required

Time in seconds after which to start the extension.

Example:

35

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audio_file
file

Uploaded audio file to be extended.

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prompt
string

Describes how the extended section should sound.

Example:

"Add a calming piano outro"

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lyrics
string

Optional lyrics for the extended segment.

Maximum length: 2000
Example:

"Let the journey fade away"

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gender
enum<string>

Voice style if vocal content is generated.

Available options:
male,
female,
neutral
Example:

"neutral"

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webhook_url
string

Callback URL for async processing results.

Example:

"https://example.com/webhook"

Response

Successfully initiated extend task

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success
boolean
​
message
string
​
task_id
string
​
conversion_id_1
string
​
conversion_id_2
string
​
eta
integer

Estimated processing time in seconds

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credit_estimate
number