Upload And Extend Audio

POST

/api/v1/generate/upload-extend

This API extends audio tracks while preserving their original style. It includes Suno's upload functionality, allowing users to upload audio files for processing. The expected result is a longer track that seamlessly continues the input style.

Parameter Usage Guide #

Character Limits

Character limits vary depending on the model version:

Model V5_5 and V5: style (max 1000 chars), title (max 100 chars), prompt (max 5000 chars)

Models V4.5PLUS and V4.5: style (max 1000 chars), title (max 100 chars), prompt (max 5000 chars)

Model V4.5ALL: style (max 1000 chars), title (max 80 chars), prompt (max 5000 chars)

Model V4: style (max 200 chars), title (max 80 chars), prompt (max 3000 chars)

When defaultParamFlag is true (Custom Parameters):

If instrumental is true: style, title, and uploadUrl are required.

If instrumental is false: style, prompt, title, and uploadUrl are required.

Character limits vary by model version (see note above).

continueAt: The time point in seconds from which to start extending (must be greater than 0 and less than the uploaded audio duration).

uploadUrl: Specifies the upload location for audio files; ensure uploaded audio does not exceed 8 minutes.

When defaultParamFlag is false (Default Parameters):

Regardless of the instrumental setting, only uploadUrl and prompt are required.

Other parameters will use the original audio's parameters.

Developer Notes #

Generated files will be retained for 14 days.

The model version used must be consistent with the source music's model version.

This feature is ideal for creating longer works by extending existing music.

The uploadUrl parameter specifies the upload location for audio files; provide a valid URL.

Optional Parameters #

vocalGender (string): Vocal gender preference. Use m for male, f for female.

styleWeight (number): Strength of adherence to the style. Range 0-1, up to 2 decimal places. Example: 0.65.

weirdnessConstraint (number): Controls creative deviation. Range 0-1, up to 2 decimal places. Example: 0.65.

audioWeight (number): Balance weight for audio features. Range 0-1, up to 2 decimal places. Example: 0.65.

personaId (string): Persona ID to apply to the generated music. Only available when Custom Mode is enabled (i.e., defaultParamFlag is true). To create one, use Generate Persona.

Callbacks

audioExtend

POST

Request

Authorization

Bearer Token

Provide your bearer token in the Authorization header when making requests to protected resources.

Example:

Authorization: Bearer ********************

or

Body Params application/jsonRequired

Generate Code

uploadUrl

string<uri>

required

The URL for uploading audio files, required regardless of whether defaultParamFlag is true or false. Ensure the uploaded audio does not exceed 8 minutes in length.

Example: https://storage.example.com/upload

defaultParamFlag

boolean

required

Enable custom mode for advanced audio generation settings.

Set to true to use custom parameter mode (requires style, title, and uploadUrl; if instrumental is false, uploadUrl and prompt are required). If instrumental is false, the prompt will be strictly used as lyrics.

Set to false to use non-custom mode (only uploadUrl required). Lyrics will be automatically generated based on the prompt.

Example: true

instrumental

boolean

required

Determines whether the audio is instrumental (without lyrics).

In custom parameter mode (customMode: true):

If true: only style, title, and uploadUrl are required.

If false: style, title, prompt (prompt will be used as exact lyrics), and uploadUrl are required.

In non-custom parameter mode (defaultParamFlag: false): does not affect required fields (only uploadUrl needed). If false, lyrics will be automatically generated.

Example: true

prompt

string

optional

Description of how the music should be extended. Required when defaultParamFlag is true. Character limits by model:

V5_5 & V5: Maximum 5000 characters

V4_5PLUS & V4_5: Maximum 5000 characters

V4_5ALL: Maximum 5000 characters

V4: Maximum 3000 characters

Example: Extend the music with more relaxing notes

style

string

optional

Music style, e.g., Jazz, Classical, Electronic. Character limits by model:

V5_5 & V5: Maximum 1000 characters

V4_5PLUS & V4_5: Maximum 1000 characters

V4_5ALL: Maximum 1000 characters

V4: Maximum 200 characters

Example: Classical

title

string

optional

Music title. Character limits by model:

V5_5 & V5: Maximum 100 characters

V4_5PLUS & V4_5: Maximum 100 characters

V4_5ALL: Maximum 80 characters

V4: Maximum 80 characters

Example: Peaceful Piano Extended

continueAt

number

required

The time point (in seconds) from which to start extending the music.

Required when defaultParamFlag is true.

Value range: greater than 0 and less than the total duration of the uploaded audio.

Specifies the position in the original track where the extension should begin.

Example: 60

model

enum<string>

required

The AI model version to use for generation.

Required for all requests.

Available options:

V5_5：Custom Models Tailored to Your Unique Taste.

V5: Superior musical expression, faster generation.

V4_5PLUS: V4.5+ delivers richer sound, new ways to create, max 8 min.

V4_5: V4.5 enables smarter prompts, faster generations, max 8 min.

V4_5ALL: V4.5ALL enables smarter prompts, faster generations, max 8 min.

V4: V4 improves vocal quality, max 4 min.

Allowed values: V4V4_5V4_5PLUSV4_5ALLV5V5_5

Example: V4

negativeTags

string

optional

Music styles to exclude from generation

Example: Relaxing Piano

callBackUrl

string<uri>

required

The URL to receive audio extension task completion updates. Required for all audio extension requests.

System will POST task status and results to this URL when audio extension completes

Callback includes extended audio files that seamlessly continue the uploaded track's style

Your callback endpoint should accept POST requests with JSON payload containing extended track results and audio URLs

For detailed callback format and implementation guide, see Audio Extension Callbacks

Alternatively, use the Get Music Details endpoint to poll task status

To ensure callback security, see Webhook Verification Guide for signature verification implementation

Example: https://api.example.com/callback

vocalGender

enum<string>

optional

Vocal gender preference for the singing voice. Optional. Use 'm' for male and 'f' for female. Based on practice, this parameter can only increase the probability but cannot guarantee adherence to male/female voice instructions.

Allowed values: mf

Example: m

styleWeight

number

optional

Strength of adherence to the specified style. Optional. Range 0-1, up to 2 decimal places.

= 0<= 1

Example: 0.65

Multiple of: 0.01

weirdnessConstraint

number

optional

Controls experimental/creative deviation. Optional. Range 0-1, up to 2 decimal places.

= 0<= 1

Example: 0.65

Multiple of: 0.01

audioWeight

number

optional

Balance weight for audio features vs. other factors. Optional. Range 0-1, up to 2 decimal places.

= 0<= 1

Example: 0.65

Multiple of: 0.01

personaId

string

optional

Only available when Custom Mode (customMode: true) is enabled. Persona ID or Voice ID to apply to the generated music. Optional. Use this to apply a specific persona style to your music generation.To generate a persona ID, use the Generate Persona endpoint to create a personalized music Persona based on generated music.To generate a Voice ID, use the Generate Voice endpoint

Example: persona_123

personaModel

enum<string>

optional

The persona model is only available for models version 5 and 5.5.

Allowed values: style_personavoice_persona

Examples

Responses

🟢200

application/json

Request successful

Bodyapplication/json

Generate Code

code

enum<integer>

optional

Response status code

200: Success - Request has been processed successfully

401: Unauthorized - Authentication credentials are missing or invalid

402: Insufficient Credits - Account does not have enough credits to perform the operation

404: Not Found - The requested resource or endpoint does not exist

409: Conflict - WAV record already exists

422: Validation Error - The request parameters failed validation checks

429: Rate Limited - Request limit has been exceeded for this resource

451: Unauthorized - Failed to fetch the image. Kindly verify any access limits set by you or your service provider.

455: Service Unavailable - System is currently undergoing maintenance

500: Server Error - An unexpected error occurred while processing the request

Allowed values: 200401402404409422429451455500

msg

string

optional

Error message when code != 200

Example: success

data

object

optional

taskId

string

optional

Task ID for tracking task status

Example: 5c79****be8e

🔴500Error

Request Request Example

Shell

JavaScript

Java

Swift

Go

PHP

Python

HTTP

C

C#

Objective-C

Ruby

OCaml

Dart

R

cURLcURL-WindowsHttpiewgetPowerShell

curl --location 'https://api.kie.ai/api/v1/generate/upload-extend' \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '{
  "uploadUrl": "https://storage.example.com/upload",
  "defaultParamFlag": true,
  "instrumental": true,
  "continueAt": 60,
  "model": "V4",
  "callBackUrl": "https://api.example.com/callback",
  "prompt": "Extend the music with more relaxing notes",
  "style": "Classical",
  "title": "Peaceful Piano Extended",
  "negativeTags": "Relaxing Piano",
  "vocalGender": "m",
  "styleWeight": 0.65,
  "weirdnessConstraint": 0.65,
  "audioWeight": 0.65,
  "personaId": "persona_123",
  "personaModel": "style_persona"
}'

Response Response Example

200 - Example 1

{
    "code": 200,
    "msg": "success",
    "data": {
        "taskId": "5c79****be8e"
    }
}