Sonauto V2 | Audio to Audio

sonauto/v2/extend

Extend an existing song

Inference

Commercial use

Partner

Schema

LLMs

Playground API

About

Extend existing songs by adding new sections to the beginning or end using Sonauto, an AI music model that transforms text into full songs with lyrics. This function takes an existing audio file and generates seamless continuations or introductions that match the style and feel of the original track.

This function accepts various combinations of prompt, tags, and lyrics to generate the extension, with the following requirements:

You must provide at least one of: prompt, tags, or lyrics
Lyrics alone are not sufficient - they must be paired with either prompt or tags
Do not provide all three inputs (prompt, tags, and lyrics) simultaneously
If tags are provided, you must also include either a prompt (to generate lyrics with AI) or your own lyrics

You can view a list of all available tags at https://sonauto.ai/tag-explorer.

1. Calling the API#

Install the client#

The client provides a convenient way to interact with the model API.

npm install --save @fal-ai/client

Migrate to @fal-ai/client

The @fal-ai/serverless-client package has been deprecated in favor of @fal-ai/client. Please check the migration guide for more information.

Setup your API Key#

Set FAL_KEY as an environment variable in your runtime.

export FAL_KEY="YOUR_API_KEY"

Submit a request#

The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.

import { fal } from "@fal-ai/client";

const result = await fal.subscribe("sonauto/v2/extend", {
  input: {
    audio_url: "https://cdn.sonauto.ai/generations2_altformats/audio_c5e63f7c-fc79-4322-808d-c09911af4713.wav",
    side: "left"
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);

2. Authentication#

The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.

API Key#

In case your app is running in an environment where you cannot set environment variables, you can set the API Key manually as a client configuration.

import { fal } from "@fal-ai/client";

fal.config({
  credentials: "YOUR_FAL_KEY"
});

Protect your API Key

When running code on the client-side (e.g. in a browser, mobile app or GUI applications), make sure to not expose your FAL_KEY. Instead, use a server-side proxy to make requests to the API. For more information, check out our server-side integration guide.

3. Queue#

Long-running requests

For long-running requests, such as training jobs or models with slower inference times, it is recommended to check the Queue status and rely on Webhooks instead of blocking while waiting for the result.

Submit a request#

The client API provides a convenient way to submit requests to the model.

import { fal } from "@fal-ai/client";

const { request_id } = await fal.queue.submit("sonauto/v2/extend", {
  input: {
    audio_url: "https://cdn.sonauto.ai/generations2_altformats/audio_c5e63f7c-fc79-4322-808d-c09911af4713.wav",
    side: "left"
  },
  webhookUrl: "https://optional.webhook.url/for/results",
});

Fetch request status#

You can fetch the status of a request to check if it is completed or still in progress.

import { fal } from "@fal-ai/client";

const status = await fal.queue.status("sonauto/v2/extend", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
  logs: true,
});

Get the result#

Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.

import { fal } from "@fal-ai/client";

const result = await fal.queue.result("sonauto/v2/extend", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);

4. Files#

Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.

Data URI (base64)#

You can pass a Base64 data URI as a file input. The API will handle the file decoding for you. Keep in mind that for large files, this alternative although convenient can impact the request performance.

Hosted files (URL)#

You can also pass your own URLs as long as they are publicly accessible. Be aware that some hosts might block cross-site requests, rate-limit, or consider the request as a bot.

Uploading files#

We provide a convenient file storage that allows you to upload files and use them in your requests. You can upload files using the client API and use the returned URL in your requests.

import { fal } from "@fal-ai/client";

const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);

Auto uploads

The client will auto-upload the file for you if you pass a binary object (e.g. File, Data).

Read more about file handling in our file upload guide.

5. Schema#

Input#

prompt string

A description of the track you want to generate. This prompt will be used to automatically generate the tags and lyrics unless you manually set them. For example, if you set prompt and tags, then the prompt will be used to generate only the lyrics.

tags list<string>

Tags/styles of the music to generate. You can view a list of all available tags at https://sonauto.ai/tag-explorer.

lyrics_prompt string

The lyrics sung in the generated song. An empty string will generate an instrumental track.

seed integer

The seed to use for generation. Will pick a random seed if not provided. Repeating a request with identical parameters (must use lyrics and tags, not prompt) and the same seed will generate the same song.

prompt_strength float

Controls how strongly your prompt influences the output. Greater values adhere more to the prompt but sound less natural. (This is CFG.) Default value: 1.8

balance_strength float

Greater means more natural vocals. Lower means sharper instrumentals. We recommend 0.7. Default value: 0.7

num_songs integer

Generating 2 songs costs 1.5x the price of generating 1 song. Also, note that using the same seed may not result in identical songs if the number of songs generated is changed. Default value: 1

output_format OutputFormatEnum

Default value: "wav"

Possible enum values: flac, mp3, wav, ogg, m4a

output_bit_rate Enum

The bit rate to use for mp3 and m4a formats. Not available for other formats.

Possible enum values: 128, 192, 256, 320

audio_url string* required

The URL of the audio file to alter. Must be a valid publicly accessible URL.

side SideEnum* required

Add more to the beginning (left) or end (right) of the song

Possible enum values: left, right

extend_duration float

Duration in seconds to extend the song. If not provided, will attempt to automatically determine.

crop_duration float

Duration in seconds to crop from the selected side before extending from that side.

{
  "prompt": "Add a beginning to the song",
  "prompt_strength": 1.8,
  "balance_strength": 0.7,
  "num_songs": 1,
  "output_format": "wav",
  "audio_url": "https://cdn.sonauto.ai/generations2_altformats/audio_c5e63f7c-fc79-4322-808d-c09911af4713.wav",
  "side": "left"
}

Output#

seed integer* required

The seed used for generation. This can be used to generate an identical song by passing the same parameters with this seed in a future request.

tags list<string>

The style tags used for generation.

lyrics string

The lyrics used for generation.

audio list<File>* required

The generated audio files.

extend_duration float* required

The duration in seconds that the song was extended by.

{
  "seed": 42,
  "audio": {
    "file_size": 22069326,
    "file_name": "sonauto.wav",
    "content_type": "audio/wav",
    "url": "https://cdn.sonauto.ai/generations2_altformats/audio_47337412-e577-42af-ae60-01a798e680ec.wav"
  }
}

Other types#

InpaintSection#

start float* required

Start time in seconds of the section to inpaint.

end float* required

End time in seconds of the section to inpaint.

File#

url string* required

The URL where the file can be downloaded from.

content_type string

The mime type of the file.

file_name string

The name of the file. It will be auto-generated if not provided.

file_size integer

The size of the file in bytes.

Table of contents

1. Calling the API

2. Authentication

3. Queue

4. Files

5. Schema

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

2. Authentication#

API Key#

Protect your API Key

3. Queue#

Long-running requests

Submit a request#

Fetch request status#

Get the result#

4. Files#

Data URI (base64)#

Hosted files (URL)#

Uploading files#

Auto uploads

5. Schema#

Input#

Output#

Other types#

InpaintSection#

File#

Related Models

Sonauto V2 Audio to Audio

Table of contents

1. Calling the API

2. Authentication

3. Queue

4. Files

5. Schema

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

2. Authentication#

API Key#

Protect your API Key

3. Queue#

Long-running requests

Submit a request#

Fetch request status#

Get the result#

4. Files#

Data URI (base64)#

Hosted files (URL)#

Uploading files#

Auto uploads

5. Schema#

Input#

Output#

Other types#

InpaintSection#

File#

Related Models