fal-ai/ace-step-1.5

Generate full songs from text prompts and lyrics—supports 50+ languages, 1000+ instruments/styles, BPM/key control, and upto 10 mins duration

Inference

Commercial use

Schema

LLMs

Playground API

About

Generate music from text description and lyrics.

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. Install the new package and update your imports — see client setup.

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("fal-ai/ace-step-1.5", {
  input: {},
  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("fal-ai/ace-step-1.5", {
  input: {},
  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("fal-ai/ace-step-1.5", {
  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("fal-ai/ace-step-1.5", {
  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

Music description/caption (style, instruments, mood). Max 512 characters. Default value: ""

lyrics string

Lyrics text with optional structure tags like [Verse], [Chorus]. Use '[Instrumental]' for instrumental music. Max 4096 characters. Default value: ""

duration float

Duration of the generated audio in seconds. Default value: 30

thinking boolean

Use 5Hz LM to generate audio codes for enhanced quality via Chain-of-Thought reasoning. Set to False for faster DiT-only generation. Default value: true

bpm integer

Beats per minute. If not specified, will be auto-detected.

key_scale string

Musical key (e.g., 'C Major', 'Am'). If not specified, will be auto-detected. Default value: ""

time_signature TimeSignatureEnum

Time signature: 2 for 2/4, 3 for 3/4, 4 for 4/4, 6 for 6/8. Default value: ""

Possible enum values: , 2, 3, 4, 6

vocal_language string

Vocal language code (e.g., 'en', 'zh', 'ja', 'ko'). Use 'unknown' for auto-detection. Default value: "unknown"

num_inference_steps integer

The number of inference steps to perform. Turbo: 8 recommended. Base: 32-64 recommended. Default value: 8

guidance_scale float

Classifier-free guidance scale. Only applies to base models, ignored by turbo. Default value: 7

shift float

Timestep shift factor. 3.0 recommended for turbo models. Default value: 3

seed integer

Random seed for reproducibility.

num_outputs integer

The number of audio samples to generate. Default value: 1

infer_method InferMethodEnum

Diffusion inference method. 'ode' (Euler) is faster and deterministic. 'sde' (stochastic) may produce varied results. Default value: "ode"

Possible enum values: ode, sde

lm_temperature float

LM sampling temperature. Higher values produce more creative/diverse output. Default value: 0.85

lm_cfg_scale float

LM classifier-free guidance scale. WARNING: Values >1.0 trigger slow step-by-step CFG generation (~10x slower). Keep at 1.0 for fast inference. Default value: 1

lm_negative_prompt string

Negative prompt for LM guidance. Helps avoid unwanted characteristics. Default value: "NO USER INPUT"

use_constrained_decoding boolean

Enable constrained decoding for structured LM output (more reliable metadata parsing). Default value: true

{
  "prompt": "A melancholic Latin trap track built on a foundation of deep 808 sub-bass and crisp, rolling hi-hats from a drum machine. A somber synth pad provides an atmospheric backdrop for the emotional male lead vocal, which is treated with noticeable auto-tune and spacious reverb.",
  "lyrics": "[Intro]\nYeah\nMe dicen ven, pero yo ya no quiero na'\n\n[Verse 1]\nNo hay más pa' ti ni de mami, ahora ves\nNo vengas con drama, lo sabes\n\n[Chorus]\nMe dicen ven, pero yo ya no quiero na'\nTe cansaste de estar pa' mí, ya no hay marcha atrás",
  "duration": 30,
  "thinking": true,
  "bpm": 92,
  "time_signature": "4",
  "vocal_language": "en",
  "num_inference_steps": 8,
  "guidance_scale": 7,
  "shift": 3,
  "num_outputs": 1,
  "infer_method": "ode",
  "lm_temperature": 0.85,
  "lm_cfg_scale": 1,
  "lm_negative_prompt": "NO USER INPUT",
  "use_constrained_decoding": true
}

Output#

audio Audio* required

Preview of the first generated audio file for quick playback

audios list<GeneratedAudio>* required

List of generated audio files

bpm integer

Detected/used BPM

duration float

Audio duration in seconds

key_scale string

Detected/used key

time_signature string

Detected/used time signature

enhanced_prompt string

LM-enhanced prompt (if thinking=True)

{
  "audio": {
    "file_size": 1995603,
    "content_type": "audio/flac",
    "file_name": "b44bec6a-c1e8-56fc-bbe5-44f9472ae8e6.flac",
    "url": "https://fal.media/files/panda/K0Fvk-Qh5ujibopcCqX_a_b44bec6a-c1e8-56fc-bbe5-44f9472ae8e6.flac"
  },
  "audios": [
    {
      "audio": {
        "file_size": 1995603,
        "content_type": "audio/flac",
        "file_name": "b44bec6a-c1e8-56fc-bbe5-44f9472ae8e6.flac",
        "url": "https://fal.media/files/panda/K0Fvk-Qh5ujibopcCqX_a_b44bec6a-c1e8-56fc-bbe5-44f9472ae8e6.flac"
      },
      "seed": 42
    }
  ],
  "bpm": 120,
  "duration": 30,
  "time_signature": "4"
}

Other types#

Audio#

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.

GeneratedAudio#

audio Audio* required

Generated audio file

seed integer* required

Seed used for this generation

fal-ai/ace-step-1.5

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#

Audio#

GeneratedAudio#