Extend - Musicgpt API Documentation

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", 
  "lyrics_section_to_extend": "New lyrics",
  "num_outputs": 1,
  "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
}

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", 
  "lyrics_section_to_extend": "New lyrics",
  "num_outputs": 1,
  "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.

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.

Request Parameters

Parameter	Type	Required	Description
`audio_file`	`UploadFile`	Optional	Upload the audio file to extend. Required if `audio_url` is not provided.
`audio_url`	`String`	Optional	Public or S3 URL to the input audio. Required if `audio_file` is not provided.
`extend_after`	`Float`	Required	Time (in seconds) after which new audio is generated.
`prompt`	`String`	Optional	Describes the desired extension sound. Example: “Add a melodic flute section”
`lyrics`	`String`	Optional	Original lyrics of song. Max 2000 characters.
`lyrics_section_to_extend`	`String`	Optional	Optional lyrics for the extended segment. Max 3000 characters.
`gender`	`String`	Optional	Voice style if vocals are generated. Must be one of `male`, `female`, `neutral`.
`num_outputs`	int	Optional	The number of outputs to generate (1 or 2 only, default : 2).
`webhook_url`	`String`	Optional	Callback URL for async result delivery.

💡 Note: You must provide either audio_file or audio_url — at least one is required.

content-type: multipart/form-data

Sample Output

Listen to the extended audio. Prompt: loud drums sound - audio input : Rose and Bruno Mars - APT extend after: 6

Download Audio

Try it Yourself

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

Sample Request

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

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:

Standard Requests (non-instrumental):

2 (webhooks) x Extend conversion details (one per version)
2 (webhooks) x Lyrics with timestamp data
1 Album Cover Image

Webhook responses include detailed metadata including task_id, conversion_id, audio files (conversion_path), lyrics etc.

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

Option 1
Option 2

audio_url

string

required

URL or S3 path to the input audio.

Example:

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

extend_after

number<float>

required

Time in seconds after which to start the extension.

Example:

35

audio_file

file

Uploaded audio file to be extended.

prompt

string

Describes how the extended section should sound.

Example:

"Add a calming piano outro"

lyrics

string

Original lyrics of song

Maximum string length: 2000

Example:

"Let the journey fade away"

lyrics_section_to_extend

string

Lyrics to be used for the extended portion(optional, max 3000 characters).

Maximum string length: 3000

gender

enum<string>

Voice style if vocal content is generated.

Available options:

male,

female,

neutral

Example:

"neutral"

num_outputs

number<integer>

The number of outputs to generate (1 or 2 only):default is 2.

webhook_url

string

Callback URL for async processing results.

Example:

"https://example.com/webhook"

Response

Successfully initiated extend task

success

boolean

message

string

task_id

string

conversion_id_1

string

conversion_id_2

string

eta

integer

Estimated processing time in seconds

credit_estimate

number<float>

Sing Over Instrumental Inpaint

​Endpoint

​Request Parameters

​Sample Output

​Try it Yourself

​Sample Request

​cURL

​Python

​Sample Response

​Success (200 OK)

​Webhook Response

​Webhook Delivery

​Standard Requests (non-instrumental):

​Common Errors

Authorizations

Body

Response

Endpoint

Request Parameters

Sample Output

Try it Yourself

Sample Request

cURL

Python

Sample Response

Success (200 OK)

Webhook Response

Webhook Delivery

Standard Requests (non-instrumental):

Common Errors