> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wav.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Extend
> This endpoint allows users to extend an existing audio file or stream by appending new audio content after a specific timestamp. The new audio is generated using a prompt (e.g., describing the desired sound) and optional lyrics.
Extend an existing audio file by generating new content after a specific timestamp.
***
## Endpoint
```http theme={null}
POST /v1/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` | `File` | Optional | Upload the audio file to extend. Required if `audio_url` is not provided. | |
| `audio_url` | `String` | Optional | URL to the audio file. | |
| `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" | |
| `title` | `String` | Optional | Title of the generated music | |
| `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). | |
| `generate_album_cover` | Boolean | Optional | false | If `true`, generate an album cover for the generated audio |
| `lyrics_timestamps` | Boolean | Optional | false | If true, generates lyric timestamps for the output track |
| `webhook_url` | `String` | Optional | Callback URL for async result delivery. | |
> **Note:** Either audio\_file or audio\_url must be provided.
> **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](/api-documentation/endpoint/extend) to play around - set your payload, hit send, and listen to the generated results live.
***
## 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.
***
## Sample Request
### cURL
```bash theme={null}
curl -X POST "https://api.wav.com/api/public/v1/extend" \
-H "accept: application/json" \
-H "Authorization: " \
-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
```python theme={null}
import requests
url = "https://api.wav.com/api/public/v1/extend"
headers = {"Authorization": ""}
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": 2,
"generate_album_cover": True,
"lyrics_timestamps": True,
"title": "My Generated Track",
"webhook_url": "https://example.com/webhook"
}
# Option 1: audio_url
data["audio_url"] = ""
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())
```
***
## Sample Response
### Success (200 OK)
```json theme={null}
{
"success": true,
"message": "Extend request submitted successfully",
"task_id": "a39f781f-e87e-4cbd-b923-aebf4aa451e6",
"conversion_id_1": "f4ecf063-6ddd-43df-bc81-9eccea5b5042",
"conversion_id_2": "49e99636-2ae7-4b5f-a907-e85a8fae95ad",
"is_flagged": false,
"reason": "",
"eta": 199,
"status": "IN_QUEUE",
"credit_estimate": 0.12,
"error_message": "",
"error_message_detail": "",
"missing_input_fields": "",
"predicted_user_intent": ""
}
```
***
## Webhook Sample Payload
Extend Webhook
```json theme={null}
{
"success": true,
"conversion_type": "Extend",
"task_id": "c287cca4-c03a-5074-b16a-b8da9d6a124c",
"conversion_id": "8725079f-bf68-5098-a6c8-6dcba44dcaa2",
"conversion_path": "https://cdn1.wav.com/conversions/api/standard/8725079f-bf68-5098-a6c8-6dcba44dcaa2/8725079f-bf68-5098-a6c8-6dcba44dcaa2.mp3",
"conversion_path_wav": "https://cdn1.wav.com/conversions/api/hq/8725079f-bf68-5098-a6c8-6dcba44dcaa2/8725079f-bf68-5098-a6c8-6dcba44dcaa2.wav",
"conversion_duration": 155.95,
"is_flagged": false,
"reason": "",
"lyrics": "[Verse]\nTurn up the sound\nLet the rhythm take control\nFeel every beat\nMoving through my soul\nLights are shining bright\nAnd we lose track of time\n\n[Chorus]\nMusic in the air\nDancing through the night\nEvery beat we share\nMakes everything feel right\nTurn it up again\nLet the whole world sing",
"lyrics_timestamped": "[{\"start\": 9880, \"end\": 35120, \"text\": \"[Verse]\", \"index\": 0}, {\"start\": 9880, \"end\": 10720, \"text\": \"Turn up the sound\", \"index\": 1}, {\"start\": 13720, \"end\": 15600, \"text\": \"Let the rhythm take control\", \"index\": 2}, {\"start\": 19200, \"end\": 20400, \"text\": \"Feel every beat\", \"index\": 3}, {\"start\": 23480, \"end\": 25400, \"text\": \"Moving through my soul\", \"index\": 4}, {\"start\": 29520, \"end\": 31440, \"text\": \"Lights are shining bright\", \"index\": 5}, {\"start\": 33320, \"end\": 35120, \"text\": \"And we lose track of time\", \"index\": 6}, {\"start\": 39640, \"end\": 54320, \"text\": \"[Chorus]\", \"index\": 7}, {\"start\": 39640, \"end\": 40120, \"text\": \"Music in the air\", \"index\": 8}, {\"start\": 41800, \"end\": 42560, \"text\": \"Dancing through the night\", \"index\": 9}, {\"start\": 44320, \"end\": 45280, \"text\": \"Every beat we share\", \"index\": 10}, {\"start\": 45600, \"end\": 47440, \"text\": \"Makes everything feel right\", \"index\": 11}, {\"start\": 49240, \"end\": 49920, \"text\": \"Turn it up again\", \"index\": 12}, {\"start\": 51720, \"end\": 54320, \"text\": \"Let the whole world sing\", \"index\": 13}]",
"title": "Rhythm Take Control",
"subtype": "remix"
}
```
Album Cover Webhook
```json theme={null}
{
"success": true,
"conversion_type": "Extend",
"task_id": "5254c422-0fab-53f0-b5e3-36abb69dd111",
"image_paths": [
"https://cdn1.wav.com/img-gen-pipeline/api/5254c422-0fab-53f0-b5e3-36abb69dd111.jpg"
],
"thumbnail_paths": [
"https://cdn1.wav.com/img-gen-pipeline/api/5254c422-0fab-53f0-b5e3-36abb69dd111_thumb.jpg"
],
"image_path": "https://cdn1.wav.com/img-gen-pipeline/api/5254c422-0fab-53f0-b5e3-36abb69dd111.jpg",
"thumbnail_path": "https://cdn1.wav.com/img-gen-pipeline/api/5254c422-0fab-53f0-b5e3-36abb69dd111_thumb.jpg",
"conversion_id_1": "eba76eae-9c77-5b09-9f2b-96a8bdef0f36",
"conversion_id_2": "1cf119ce-a78c-500b-ad43-4b1f598507cb",
"album_cover_generator_output": true,
"subtype": "album_cover_generation",
}
```
Lyrics Timestamp Webhook
```json theme={null}
{
"success": true,
"conversion_type": "Extend",
"task_id": "c287cca4-c03a-5074-b16a-b8da9d6a124c",
"conversion_id": "8725079f-bf68-5098-a6c8-6dcba44dcaa2",
"subtype": "lyrics_timestamped",
"lyrics_timestamped": "[{\"start\": 9880, \"end\": 35120, \"text\": \"[Verse]\", \"index\": 0}, {\"start\": 9880, \"end\": 10720, \"text\": \"Turn up the sound\", \"index\": 1}, {\"start\": 13720, \"end\": 15600, \"text\": \"Let the rhythm take control\", \"index\": 2}, {\"start\": 19200, \"end\": 20400, \"text\": \"Feel every beat\", \"index\": 3}, {\"start\": 23480, \"end\": 25400, \"text\": \"Moving through my soul\", \"index\": 4}, {\"start\": 29520, \"end\": 31440, \"text\": \"Lights are shining bright\", \"index\": 5}, {\"start\": 33320, \"end\": 35120, \"text\": \"And we lose track of time\", \"index\": 6}, {\"start\": 39640, \"end\": 54320, \"text\": \"[Chorus]\", \"index\": 7}, {\"start\": 39640, \"end\": 40120, \"text\": \"Music in the air\", \"index\": 8}, {\"start\": 41800, \"end\": 42560, \"text\": \"Dancing through the night\", \"index\": 9}, {\"start\": 44320, \"end\": 45280, \"text\": \"Every beat we share\", \"index\": 10}, {\"start\": 45600, \"end\": 47440, \"text\": \"Makes everything feel right\", \"index\": 11}, {\"start\": 49240, \"end\": 49920, \"text\": \"Turn it up again\", \"index\": 12}, {\"start\": 51720, \"end\": 54320, \"text\": \"Let the whole world sing\", \"index\": 13}]"
}
```
***
## 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.
## OpenAPI
````yaml POST /v1/extend
openapi: 3.1.0
info:
title: WAV API
version: 1.0.0
description: API for retrieving conversion details by ID.
servers:
- url: https://api.wav.com/api/public
description: Production server
security: []
paths:
/v1/extend:
post:
summary: Extend Audio Using Prompt and Optional Lyrics
description: >-
This endpoint allows users to extend an existing audio file or stream by
appending new audio content after a specific timestamp. The new audio is
generated using a prompt (e.g., describing the desired sound) and
optional lyrics.
requestBody:
required: true
content:
multipart/form-data:
schema:
type: object
properties:
audio_file:
type: string
format: binary
description: Uploaded audio file to be extended.
audio_url:
type: string
description: 'Input audio URL (supported format: YouTube URL).'
example: https://mybucket.s3.amazonaws.com/song.mp3
extend_after:
type: number
format: float
description: Time in seconds after which to start the extension.
example: 35
prompt:
type: string
description: Describes how the extended section should sound.
example: Add a calming piano outro
lyrics:
type: string
description: Original lyrics of song
example: Let the journey fade away
maxLength: 2000
lyrics_section_to_extend:
type: string
description: >-
Lyrics to be used for the extended portion(optional, max
3000 characters).
maxLength: 3000
gender:
type: string
description: Voice style if vocal content is generated.
enum:
- male
- female
- neutral
example: neutral
title:
type: string
description: Title of the generated music track
num_outputs:
type: number
format: integer
description: >-
The number of outputs to generate (1 or 2 only):default is
2.
generate_album_cover:
type: boolean
description: Whether to generate an album cover for the generated audio
default: false
lyrics_timestamps:
type: boolean
description: Whether to generate timestamps for the lyrics
default: false
webhook_url:
type: string
description: Callback URL for async processing results.
example: https://example.com/webhook
required:
- extend_after
anyOf:
- required:
- audio_url
- required:
- audio_file
responses:
'200':
description: Successfully initiated extend task
content:
application/json:
schema:
type: object
properties:
success:
type: boolean
message:
type: string
task_id:
type: string
conversion_id_1:
type: string
conversion_id_2:
type: string
is_flagged:
type: boolean
reason:
type: string
eta:
type: integer
description: Estimated processing time in seconds
status:
type: string
credit_estimate:
type: number
format: float
error_message:
type: string
error_message_detail:
type: string
missing_input_fields:
type: string
predicted_user_intent:
type: string
example:
success: true
message: Extend request submitted successfully
task_id: a39f781f-e87e-4cbd-b923-aebf4aa451e6
conversion_id_1: f4ecf063-6ddd-43df-bc81-9eccea5b5042
conversion_id_2: 49e99636-2ae7-4b5f-a907-e85a8fae95ad
is_flagged: false
reason: ''
eta: 199
status: IN_QUEUE
credit_estimate: 0.12
error_message: ''
error_message_detail: ''
missing_input_fields: ''
predicted_user_intent: ''
'422':
description: Validation Error
content:
application/json:
schema:
type: object
properties:
success:
type: boolean
example: false
message:
type: string
example: audio_file or audio_url and extend_after are required.
'500':
description: Server Error
content:
application/json:
schema:
type: object
properties:
success:
type: boolean
example: false
message:
type: string
example: Internal Server Error
security:
- ApiKeyAuth: []
x-codeSamples:
- lang: Python
source: >-
import requests
url = "https://api.wav.com/api/public/v1/extend"
headers = {"Authorization": ""}
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,
"title": "My Generated Track",
"webhook_url": "https://example.com/webhook"
}
# Option 1: audio_url
data["audio_url"] = ""
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())
components:
securitySchemes:
ApiKeyAuth:
type: apiKey
in: header
name: Authorization
````