ace modelsaudio generation api

ace/ace-step/audio-outpaint

Name: ACE-Step Audio Outpaint
Author: ace

Ace Step Audio Outpaint by ace - advanced AI model for audio-to-audio. Delivers high-quality results with fast inference, suitable for both creative and production workflows.

Input

Audio Url(string)

URL of the audio file to be outpainted.

Lyrics(string)

Lyrics to be sung in the audio. If not provided or if [inst] or [instrumental] is the content of this field, no lyrics will be sung. Use control structures like [verse], [chorus] and [bridge] to control the structure of the song.

Seed(integer)

Random seed for reproducibility. If not provided, a random seed will be used.

Tags(string)

Comma-separated list of genre tags to control the style of the generated audio.

Granularity Scale(integer)

-100100

Granularity scale for the generation process. Higher values can reduce artifacts. Range: -100 to 100.

Extend Before Duration(number)

0240

Duration in seconds to extend the audio from the start. Range: 0 to 240.

Tag Guidance Scale(number)

010

Tag guidance scale for the generation. Range: 0 to 10.

Guidance Type(string)

Type of CFG to use for the generation process. Allowed values: cfg, apg, cfg_star.

Guidance Interval(number)

Guidance interval for the generation. 0.5 means only apply guidance in the middle steps (0.25 * infer_steps to 0.75 * infer_steps) Range: 0 to 1.

Minimum Guidance Scale(number)

0200

Minimum guidance scale for the generation after the decay. Range: 0 to 200.

Lyric Guidance Scale(number)

010

Lyric guidance scale for the generation. Range: 0 to 10.

Number Of Steps(integer)

360

Number of steps to generate the audio. Range: 3 to 60.

Extend After Duration(number)

0240

Duration in seconds to extend the audio from the end. Range: 0 to 240.

Guidance Interval Decay(number)

Guidance interval decay for the generation. Guidance scale will decay from guidance_scale to min_guidance_scale in the interval. 0.0 means no decay. Range: 0 to 1.

Guidance Scale(number)

Range: 0 to 200.

Idle

Example output — click Run to generate your own

Production endpoint

Send your first request

OpenAI-compatible endpoint with unified authentication and usage tracking.

POSThttps://api.sandbase.ai/v1/run

Model IDace/ace-step/audio-outpaint

Input Schema

15 parameters · 0 required · 15 optional

Parameter	Type	Required	Description
`seed`	integer	Optional	Random seed for reproducibility. If not provided, a random seed will be used.
`tags`	string	Optional	Comma-separated list of genre tags to control the style of the generated audio.
`audio`	string	Optional	URL of the audio file to be outpainted.
`lyrics`	string	Optional	Lyrics to be sung in the audio. If not provided or if [inst] or [instrumental] is the content of this field, no lyrics will be sung. Use control structures like [verse], [chorus] and [bridge] to control the structure of the song. · Default: ""
`guidance_type`	string	Optional	Type of CFG to use for the generation process. · Options: cfg, apg, cfg_star · Default: "apg" cfgapgcfg_star
`guidance_scale`	number	Optional	Min: 0 · Max: 200 · Default: 15
`number_of_steps`	integer	Optional	Number of steps to generate the audio. · Min: 3 · Max: 60 · Default: 27
`granularity_scale`	integer	Optional	Granularity scale for the generation process. Higher values can reduce artifacts. · Min: -100 · Max: 100 · Default: 10
`guidance_interval`	number	Optional	Guidance interval for the generation. 0.5 means only apply guidance in the middle steps (0.25 * infer_steps to 0.75 * infer_steps) · Min: 0 · Max: 1 · Default: 0.5
`tag_guidance_scale`	number	Optional	Tag guidance scale for the generation. · Min: 0 · Max: 10 · Default: 5
`lyric_guidance_scale`	number	Optional	Lyric guidance scale for the generation. · Min: 0 · Max: 10 · Default: 1.5
`extend_after_duration`	number	Optional	Duration in seconds to extend the audio from the end. · Min: 0 · Max: 240 · Default: 30
`extend_before_duration`	number	Optional	Duration in seconds to extend the audio from the start. · Min: 0 · Max: 240 · Default: 0
`minimum_guidance_scale`	number	Optional	Minimum guidance scale for the generation after the decay. · Min: 0 · Max: 200 · Default: 3
`guidance_interval_decay`	number	Optional	Guidance interval decay for the generation. Guidance scale will decay from guidance_scale to min_guidance_scale in the interval. 0.0 means no decay. · Min: 0 · Max: 1 · Default: 0

Output Schema

Field	Type	Description
`id`	string	Unique identifier for the generation task
`status`	string	Task status: pending, running, completed, failed, timeout
`model`	string	Model used for the generation
`outputs`	array	Array of output items
`outputs[].url`	string	URL of the generated artifact
`outputs[].content_type`	string	MIME type (e.g. image/png, video/mp4)
`error`	object \| null	Error details if failed, null on success
`error.type`	string	Machine-readable error type code
`error.message`	string	Human-readable error description

Async Workflow

This model uses asynchronous execution. Submit a request and poll for the result.

Submit — POST to /v1/run, receive an id
Poll — GET /v1/run/{id} until status is completed, failed, or timeout
Retrieve — Read outputs from the completed response

Code Examples

Ready-to-run snippets

# Step 1: Submit
curl -X POST https://api.sandbase.ai/v1/run \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
  "model": "ace/ace-step/audio-outpaint",
  "tags": "lofi, hiphop, drum and bass, trap, chill",
  "audio": "https://storage.googleapis.com/falserverless/example_inputs/ace-step-audio-to-audio.wav",
  "lyrics": "",
  "guidance_type": "apg",
  "guidance_scale": 15,
  "number_of_steps": 27,
  "granularity_scale": 10,
  "guidance_interval": 0.5,
  "tag_guidance_scale": 5,
  "lyric_guidance_scale": 1.5,
  "extend_after_duration": 30,
  "extend_before_duration": 0,
  "minimum_guidance_scale": 3,
  "guidance_interval_decay": 0,
  "prompt": "a beautiful sunset over mountains"
}'

# Step 2: Poll result (replace <id>)
curl https://api.sandbase.ai/v1/run/<id> \
  -H "Authorization: Bearer YOUR_API_KEY"

← Back to ACE-Step Audio Outpaint

API README

ACE-Step Audio Outpaint

ACE-Step Audio Outpaint extends an existing recording before its opening, after its ending, or in both directions. It uses the supplied audio as musical context so new material can continue the established style rather than starting as an unrelated track.

Extension lengths can be set independently up to four minutes, while tags, lyrics, seed, inference steps, and guidance controls shape the continuation. This makes the route useful for lengthening cues, adding intros or outros, and developing a short idea into a fuller arrangement.

Highlights

Bidirectional extension. Adds new music before or after the source recording with independent duration controls.

Source-aware continuation. Uses the original audio to carry forward its musical identity and production context.

Intro and outro creation. Expands short cues with openings, endings, transitions, or additional arrangement space.

Controlled composition. Tags, lyrics, seed, steps, and guidance settings direct how the extension develops.

Pricing

Billing unit	Price
Per generated second	$0.0002

When to Use

✅ Good fit	❌ Consider alternatives
Existing audio needs a new intro, outro, or continuation	Only an internal passage needs replacement
A managed asynchronous result is suitable for the production pipeline	A synchronous, interactive editor is essential
The documented controls cover the required duration, framing, or format	The project needs controls outside this endpoint's schema
Creative iteration benefits from a repeatable request structure	Exact deterministic pixels, frames, geometry, or samples are mandatory
A finished downloadable media asset is the desired deliverable	Editable source layers or a native project file are required

Prompt Guide

For music generation, state the intended result first, then add the subject or source treatment, progression, style, and delivery constraints. Keep one creative variable per phrase, use the documented field names for controls, and change one setting at a time when comparing results.

{
  "audio": "https://storage.googleapis.com//example_inputs/ace-step-audio-to-audio.wav"
}

Technical Specs

Spec	Value
Model ID	`ace/ace-step/audio-outpaint`
Inputs	audio, extend_after_duration, extend_before_duration, granularity_scale, guidance_interval, guidance_interval_decay, guidance_scale, guidance_type, lyric_guidance_scale, lyrics, minimum_guidance_scale, number_of_steps, seed, tag_guidance_scale, tags
Required inputs	None
Output fields	content_type, url
Execution	Async (submit, then poll for result)

Related Models

ace/ace-step — Compare a nearby route in the same local model family.
ace/ace-step/audio-inpaint — Compare a nearby route in the same local model family.
ace/ace-step/audio-to-audio — Compare a nearby route in the same local model family.