Question 1

What is the difference between xl-turbo and xl-sft?

Accepted Answer

xl-turbo is distilled for 8-step inference without classifier-free guidance: fastest, ideal for drafts. xl-sft is the supervised fine-tuned checkpoint running 50 steps with CFG (default guidance 2.0): highest quality for final renders. Select per request with the model field; both share the same LM 4B planner.

Question 2

How do I write good prompts for it?

Accepted Answer

Put style in caption (genre, instruments, mood, BPM, vocal style; be specific) and vocal content in lyrics with section tags like [Verse 1], [Chorus], [Bridge], or [Instrumental]. You can also POST /format to have the LM enhance a rough caption/lyrics pair, or set use_format: true on /generate.

Question 3

What does the thinking parameter do?

Accepted Answer

With thinking: true (the default and recommendation), the shared acestep-5Hz-lm-4B planner runs first: it plans BPM, key, duration, and semantic audio codes via Chain-of-Thought before the DiT synthesizes audio. This is the core of ACE-Step 1.5's hybrid LM+DiT design.

Question 4

Why did my vocal track come out instrumental?

Accepted Answer

The LM caption-rewrite step can turn a prompt instrumental. When you pass real lyrics, set use_cot_caption: false (per the chute readme) so the planner keeps your vocal intent, and make sure lyrics contains tagged vocal sections rather than the default [Instrumental].

Question 5

How is the request body structured?

Accepted Answer

Unlike most Chutes media endpoints, this chute wraps the body: nest all fields under a top-level args object, e.g. {"args": {"caption": "...", "lyrics": "..."}}. The response from /generate is raw audio bytes (mp3 by default) unless return_json: true.

Question 6

Can I use generated music commercially?

Accepted Answer

Yes. The model is MIT-licensed and the ACE-Step 1.5 card states it is trained on licensed, royalty-free/public-domain, and synthetic data specifically so generated music can be used for commercial purposes.

Question 7

Can it edit existing audio?

Accepted Answer

Partially. task_type cover restyles existing audio (send src_audio_b64, tune audio_cover_strength), and repaint regenerates a chosen time window (repainting_start/repainting_end). Stem extraction, lego, and complete require the xl-base checkpoint, which is not loaded on this chute and returns 400.

Question 8

How long can a track be and what formats are supported?

Accepted Answer

10 to 240 seconds per the chute readme, with a 120-second endpoint default. Note: in live testing (July 2026) the deployment returned ~120-second tracks regardless of the duration value sent, so treat shorter/longer requests as best-effort. Output formats: mp3 (default), wav, flac, opus, aac, and wav32 via the audio_format field.

ACE Step 15 Music Generator

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ACE Step 15 Music Generator

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