ACE Step Audio Outpaint | AI Voice Conversion API

ACE-Step Audio Outpaint

Extend your audio tracks seamlessly with AI-powered music generation. Upload any audio clip and let the model generate new content before or after it — perfectly matching the style, rhythm, and mood of your original track.

Why It Sounds Great

Style-aware generation: Uses tag-based guidance to match genres like lofi, hiphop, trap, drum and bass, and more.
Seamless transitions: Generated audio blends naturally with your original track without abrupt cuts or mismatched beats.
Bidirectional extension: Extend audio at the beginning, end, or both directions simultaneously.
Lyrics support: Optionally provide lyrics to guide vocal generation in extended sections.
Reproducible results: Use the seed parameter to recreate exact outputs or explore variations.

Parameters

Parameter	Required	Description
audio	Yes	Source audio file (upload or public URL).
tags	Yes	Comma-separated style tags to guide generation (e.g., "lofi, hiphop, chill, trap").
extend_before_duration	No	Seconds to generate before the original audio. Default: 0.
extend_after_duration	No	Seconds to generate after the original audio. Default: 30.
lyrics	No	Optional lyrics to guide vocal generation in extended sections.
seed	No	Random seed for reproducibility. Use -1 for random.

How to Use

Upload your audio — drag and drop or paste a public URL.
Add style tags — describe the genre and mood (e.g., "lofi, hiphop, chill").
Set extension duration:

Use extend_after_duration to add time at the end.
Use extend_before_duration to add time at the beginning.

Add lyrics (optional) — provide text if you want vocals in the extended section.
Set seed (optional) — use -1 for random, or a specific number for reproducible results.
Run — click the button and wait for generation.
Download — preview and save your extended audio.

Pricing

Per-second billing based on total output duration.

Metric	Cost
Per second	$0.0002

Billing Formula

Total cost = (original audio duration + extend_before_duration + extend_after_duration) × $0.0002

Examples

Original	Extend Before	Extend After	Total Duration	Total Cost
60s	0s	30s	90s	$0.018
90s	10s	30s	130s	$0.026
120s	0s	60s	180s	$0.036
180s	30s	30s	240s	$0.048

Best Use Cases

Music Production — Extend loops, intros, or outros for full-length tracks.
Content Creation — Generate longer background music for videos and podcasts.
DJ & Remix Work — Create extended mixes or seamless transitions between tracks.
Game & Media Audio — Produce adaptive music that can loop or extend dynamically.
Songwriting — Explore new directions by extending existing ideas with AI assistance.

Pro Tips for Best Results

Use descriptive, specific tags — "lofi, hiphop, jazzy, chill, piano" works better than just "music".
For consistent style, keep the original audio and extension durations balanced.
Experiment with different seeds to find the perfect variation.
When using lyrics, match the syllable count and rhythm to the expected musical phrasing.
Start with shorter extensions (15-30s) to test the style match before generating longer segments.

Notes

If using a URL, ensure it is publicly accessible. A preview player in the interface confirms successful loading.
Processing time scales with total output duration.
For best results, use clean source audio with consistent tempo and style.

Ace Step Audio Outpaint API — Quick start

Grab a WaveSpeedAI API key, then call POST https://api.wavespeed.ai/api/v3/wavespeed-ai/ace-step/audio-outpaint with your input as JSON. The endpoint returns a prediction id; poll the prediction endpoint until status flips to completed, then read the output URL from data.outputs[0]. Examples for Ace Step Audio Outpaint below.

HTTP example

# Submit the prediction
curl -X POST "https://api.wavespeed.ai/api/v3/wavespeed-ai/ace-step/audio-outpaint" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $WAVESPEED_API_KEY" \
  -d '{
    "audio": "https://example.com/your-audio.mp3",
    "extend_before_duration": 0,
    "extend_after_duration": 30,
    "seed": -1
}'

# Response includes a prediction id. Poll for the result:
curl -X GET "https://api.wavespeed.ai/api/v3/predictions/{request_id}/result" \
  -H "Authorization: Bearer $WAVESPEED_API_KEY"

# When status is "completed", read the output from data.outputs[0].

Node.js example

// npm install wavespeed
const WaveSpeed = require('wavespeed');

const client = new WaveSpeed(); // reads WAVESPEED_API_KEY from env

const result = await client.run("wavespeed-ai/ace-step/audio-outpaint", {
        "audio": "https://example.com/your-audio.mp3",
        "extend_before_duration": 0,
        "extend_after_duration": 30,
        "seed": -1
});

console.log(result.outputs[0]); // → URL of the generated output

Python example

# pip install wavespeed
import wavespeed

output = wavespeed.run(
    "wavespeed-ai/ace-step/audio-outpaint",
    {
    "audio": "https://example.com/your-audio.mp3",
    "extend_before_duration": 0,
    "extend_after_duration": 30,
    "seed": -1
}
)

print(output["outputs"][0])  # → URL of the generated output

Ace Step Audio Outpaint API — Frequently asked questions

What is the Ace Step Audio Outpaint API?

Ace Step Audio Outpaint is a WaveSpeedAI model for AI inference, exposed as a REST API on WaveSpeedAI. ACE-Step Audio Outpaint generates seamless start or end extensions that match the original, ideal for intros, outros and longer tracks. Ready-to-use REST inference API, best performance, no coldstarts, affordable pricing. You can call it programmatically or try it from the playground above.

How do I call the Ace Step Audio Outpaint API?

POST your input parameters to the model's REST endpoint (shown in the API tab of this playground) with your WaveSpeedAI API key in the Authorization header. Submission returns a prediction ID; poll the prediction endpoint until status flips to "completed", then read the output URL from the result. The playground generates a ready-to-paste code sample in Python, JavaScript, or cURL for whatever inputs you've set. Full request/response shape is documented at https://wavespeed.ai/docs/docs-api/wavespeed-ai/ace-step-audio-outpaint.

How much does Ace Step Audio Outpaint cost per run?

Ace Step Audio Outpaint starts at $0.000 per run. That figure is the base price — the final charge scales with the parameters you set in the form (output size, length, count, references, or whatever knobs this model exposes), so a higher-quality or larger output costs more than a minimal one. The exact cost for your current input is shown live next to the Generate button before you submit, and the actual per-call charge is recorded on the prediction afterwards.

What inputs does Ace Step Audio Outpaint accept?

Key inputs: `audio`, `seed`, `extend_after_duration`, `extend_before_duration`, `lyrics`, `tags`. The full JSON schema (types, defaults, allowed values) is rendered above the Generate button and mirrored in the API reference at https://wavespeed.ai/docs/docs-api/wavespeed-ai/ace-step-audio-outpaint.

How do I get started with the Ace Step Audio Outpaint API?

Sign up for a free WaveSpeedAI account to claim starter credits, copy your API key from /accesskey, then call the endpoint shown in the API tab of the playground. The playground also auto-generates a code sample in Python, JavaScript, or cURL for the parameters you've set.

Can I use Ace Step Audio Outpaint outputs commercially?

Commercial usage rights depend on the model's license, set by its provider (WaveSpeedAI). The license summary appears on the model card above; see WaveSpeedAI's Terms of Service for platform-level conditions.

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