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name: acestep description: AI music generation with ACE-Step 1.5 — background music, vocal tracks, covers, stem extraction, audio repainting, and continuation for video production. Use when generating music, soundtracks, jingles, or working with audio stems. Triggers include background music, soundtrack, jingle, music generation, stem extraction, cover, style transfer, repaint, continuation, or musical composition tasks.

ACE-Step 1.5 Music Generation

Open-source music generation via tools/music_gen.py.

Cloud providers:

• acemusic (default) — Official ACE-Step cloud API with XL Turbo (4B) model + 5Hz LM thinking mode. Free API key from acemusic.ai/api-key. No GPU required.
• modal — Self-hosted ACE-Step 1.5 XL Turbo (4B DiT, no LM) on Modal A10G. Requires MODAL_MUSIC_GEN_ENDPOINT_URL.
• runpod — Self-hosted ACE-Step 2B Turbo on RunPod. Requires RUNPOD_ACESTEP_ENDPOINT_ID.

Setup

# acemusic (recommended — free, best quality, no GPU)
echo "ACEMUSIC_API_KEY=your_key" >> .env
# Get key at https://acemusic.ai/api-key

# Self-hosted (optional fallback)
uv run tools/music_gen.py --setup             # RunPod
uv run modal deploy docker/modal-music-gen/app.py    # Modal

Quick Reference

# Basic generation (uses acemusic XL Turbo by default)
uv run tools/music_gen.py --prompt "Upbeat tech corporate" --duration 60 --output bg.mp3

# Generate 4 variations, pick the best
uv run tools/music_gen.py --prompt "Calm ambient piano" --duration 30 --variations 4 --output ambient.mp3

# Fast mode (disable thinking)
uv run tools/music_gen.py --no-thinking --prompt "Quick draft" --duration 30 --output draft.mp3

# With musical control
uv run tools/music_gen.py --prompt "Calm ambient piano" --duration 30 --bpm 72 --key "D Major" --output ambient.mp3

# Scene presets (video production)
uv run tools/music_gen.py --preset corporate-bg --duration 60 --output bg.mp3
uv run tools/music_gen.py --preset tension --duration 20 --output problem.mp3
uv run tools/music_gen.py --preset cta --brand digital-samba --duration 15 --output cta.mp3

# Vocals with lyrics
uv run tools/music_gen.py --prompt "Indie pop jingle" --lyrics "[verse]\nBuild it better\nShip it faster" --duration 30 --output jingle.mp3

# Cover / style transfer
uv run tools/music_gen.py --cover --reference theme.mp3 --prompt "Jazz piano version" --duration 60 --output jazz_cover.mp3

# Repaint a weak section
uv run tools/music_gen.py --repaint --input track.mp3 --repaint-start 15 --repaint-end 25 --prompt "Guitar solo" --output fixed.mp3

# Continue from existing audio
uv run tools/music_gen.py --continuation --input track.mp3 --prompt "Continue with jazz piano" --output extended.mp3

# Stem extraction
uv run tools/music_gen.py --extract vocals --input mixed.mp3 --output vocals.mp3

# Fall back to self-hosted
uv run tools/music_gen.py --cloud modal --prompt "Background music" --duration 60 --output bg.mp3

Fixing "Samey" Output

If generated music sounds repetitive or lacks variety, try these in order:

1. Use acemusic cloud (default) — XL Turbo 4B plus the 5Hz LM; Modal runs the same XL Turbo DiT but without the LM, RunPod is still 2B
2. Keep thinking mode on (default for acemusic) — the 5Hz LM enriches sparse prompts into detailed musical descriptions
3. Generate variations — --variations 4 generates 4 takes, pick the best
4. Use stochastic inference — --infer-method sde adds randomness (same seed gives different results)
5. Vary BPM and key across scenes — don't use the same preset for every scene
6. Write sparser prompts — "Upbeat indie rock" gives the model more creative freedom than a hyper-detailed description
7. Vary seeds — omit --seed to let each generation be unique

Creating a Song (Step by Step)

1. Instrumental background track (simplest)

uv run tools/music_gen.py --prompt "Upbeat indie rock, driving drums, jangly guitar" --duration 60 --bpm 120 --key "G Major" --output track.mp3

2. Song with vocals and lyrics

Write lyrics in a temp file or pass inline. Use structure tags to control song sections.

# Write lyrics to a file first (recommended for longer songs)
cat > /tmp/lyrics.txt << 'LYRICS'
[Verse 1]
Walking through the morning light
Coffee in my hand feels right
Another day to build and dream
Nothing's ever what it seems

[Chorus - anthemic]
WE KEEP MOVING FORWARD
Through the noise and doubt
We keep moving forward
That's what it's about

[Verse 2]
Screens are glowing late at night
Shipping code until it's right
The deadline's close but so are we
Almost there, just wait and see

[Chorus - bigger]
WE KEEP MOVING FORWARD
Through the noise and doubt
We keep moving forward
That's what it's about

[Outro - fade]
(Moving forward...)
LYRICS

# Generate the song
uv run tools/music_gen.py \
  --prompt "Upbeat indie rock anthem, male vocal, driving drums, electric guitar, studio polish" \
  --lyrics "$(cat /tmp/lyrics.txt)" \
  --duration 60 \
  --bpm 128 \
  --key "G Major" \
  --output my_song.mp3

3. Repaint a weak section

If the chorus sounds weak, regenerate just that section:

uv run tools/music_gen.py --repaint --input my_song.mp3 --repaint-start 20 --repaint-end 35 --prompt "Powerful anthemic chorus, big drums" --output fixed.mp3

4. Continue/extend a track

uv run tools/music_gen.py --continuation --input my_song.mp3 --prompt "Continue with gentle acoustic outro" --output extended.mp3

Key tips for good results

• Caption = overall style (genre, instruments, mood, production quality)
• Lyrics = temporal structure (verse/chorus flow, vocal delivery)
• UPPERCASE in lyrics = high vocal intensity
• Parentheses = background vocals: "We rise (together)"
• Keep 6-10 syllables per line for natural rhythm
• Don't describe the melody in the caption — describe the sound and feeling
• Use --seed to lock randomness when iterating on prompt/lyrics

Controlling vocal gender

The model doesn't reliably follow "female vocal" or "male vocal" on its own. Use both of these together:

1. In the prompt: Be explicit — "solo female singer, alto voice" or "female vocalist only, breathy intimate voice". Adding an artist reference helps (e.g., "Brandi Carlile style").
2. In the lyrics: Add [female vocal] tags before each section:

[female vocal]
[Verse 1]
Walking through the morning light...

[female vocal]
[Chorus - anthemic]
WE KEEP MOVING FORWARD...

Just saying "female vocal" in the prompt alone is often ignored. The combination of prompt + lyrics tags is what works.

Duets and vocal trading

For duets with male/female vocals trading verses, use both the prompt and per-section lyrics tags:

• Prompt: "duet, male and female vocals trading verses, warm harmonies on chorus"
• Lyrics: Tag each section with who sings it:

[Verse 1 - male vocal, storytelling]
First verse lyrics here...

[Chorus - male and female duet, harmonies]
Chorus lyrics here...

[Verse 2 - female vocal, wry]
Second verse lyrics here...

[Bridge - male vocal, spoken]
Spoken bridge...

[Bridge - female vocal, sung]
Sung response...

This reliably produces vocal trading between sections and harmonies on shared parts.

Scene Presets

Preset	BPM	Key	Use Case
corporate-bg	110	C Major	Professional background, presentations
upbeat-tech	128	G Major	Product launches, tech demos
ambient	72	D Major	Overview slides, reflective content
dramatic	90	D Minor	Reveals, announcements
tension	85	A Minor	Problem statements, challenges
hopeful	120	C Major	Solution reveals, resolutions
cta	135	E Major	Call to action, closing energy
lofi	85	F Major	Screen recordings, coding demos

Task Types

text2music (default)

Generate music from text prompt + optional lyrics.

cover

Style transfer from reference audio. Control blend with --cover-strength (0.0-1.0):

• 0.2 — Loose style inspiration (more creative freedom)
• 0.5 — Balanced style transfer
• 0.7 — Close to original structure (default)
• 1.0 — Maximum fidelity to source

extract

Stem separation — isolate individual tracks from mixed audio. Tracks: vocals, drums, bass, guitar, piano, keyboard, strings, brass, woodwinds, other

Upstream lists extract as a base-model task (acestep-v15-base / -xl-base). The turbo DiTs the self-hosted endpoints serve (XL Turbo on Modal, 2B Turbo on RunPod) don't support it, so expect weak stems there.

repainting (acemusic only)

Regenerate a specific time segment within existing audio while preserving the rest.

uv run tools/music_gen.py --repaint --input track.mp3 --repaint-start 15 --repaint-end 25 --prompt "Guitar solo" --output fixed.mp3

continuation (acemusic only)

Extend existing audio by continuing from where it ends.

uv run tools/music_gen.py --continuation --input track.mp3 --prompt "Continue with jazz piano" --output extended.mp3

Prompt Engineering

Caption Writing — Layer Dimensions

Write captions by layering multiple descriptive dimensions rather than single-word descriptions.

Dimensions to include:

• Genre/Style: pop, rock, jazz, electronic, lo-fi, synthwave, orchestral
• Emotion/Mood: melancholic, euphoric, dreamy, nostalgic, intimate, tense
• Instruments: acoustic guitar, synth pads, 808 drums, strings, brass, piano
• Timbre: warm, crisp, airy, punchy, lush, polished, raw
• Era: "80s synth-pop", "modern indie", "classical romantic"
• Production: lo-fi, studio-polished, live recording, cinematic
• Vocal: breathy, powerful, falsetto, raspy, spoken word (or "instrumental")

Good: "Slow melancholic piano ballad with intimate female vocal, warm strings building to powerful chorus, studio-polished production" Bad: "Sad song"

Key Principles

1. Specificity over vagueness — describe instruments, mood, production style
2. Avoid contradictions — don't request "classical strings" and "hardcore metal" simultaneously
3. Repetition reinforces priority — repeat important elements for emphasis
4. Sparse captions = more creative freedom — detailed captions constrain the model
5. Use metadata params for BPM/key — don't write "120 BPM" in the caption, use --bpm 120

Lyrics Formatting

Structure tags (use in lyrics, not caption):

[Intro]
[Verse]
[Chorus]
[Bridge]
[Outro]
[Instrumental]
[Guitar Solo]
[Build]
[Drop]
[Breakdown]

Vocal control (prefix lines or sections):

[raspy vocal]
[whispered]
[falsetto]
[powerful belting]
[harmonies]
[ad-lib]

Energy indicators:

• UPPERCASE = high intensity ("WE RISE ABOVE")
• Parentheses = background vocals ("We rise (together)")
• Keep 6-10 syllables per line within sections for natural rhythm

Video Production Integration

Music for Scene Types

Scene	Preset	Duration	Notes
Title	dramatic or ambient	3-5s	Short, mood-setting
Problem	tension	10-15s	Dark, unsettling
Solution	hopeful	10-15s	Relief, optimism
Demo	lofi or corporate-bg	30-120s	Non-distracting, matches demo length
Stats	upbeat-tech	8-12s	Building credibility
CTA	cta	5-10s	Maximum energy, punchy
Credits	ambient	5-10s	Gentle fade-out

Timing Workflow

1. Plan scene durations first (from voiceover script)
2. Generate music to match: --duration <scene_seconds>
3. Music duration is precise (within 0.1s of requested)
4. For background music spanning multiple scenes: generate one long track

Combining with Voiceover

Background music should be mixed at 10-20% volume in Remotion:

<Audio src={staticFile('voiceover.mp3')} volume={1} />
<Audio src={staticFile('bg-music.mp3')} volume={0.15} />

For music under narration: use instrumental presets (corporate-bg, ambient, lofi). For music-forward scenes (title, CTA): can use higher volume or vocal tracks.

Brand Consistency

Use --brand <name> to load hints from brands/<name>/brand.json. Use --cover --reference brand_theme.mp3 to create variations of a brand's sonic identity. For consistent sound across a project: fix the seed (--seed 42) and vary only duration/prompt.

Advanced Parameters

Flag	Default	Description
--thinking	on (acemusic)	5Hz LM enriches prompts and generates audio codes
--no-thinking	-	Faster generation, skip LM reasoning
--variations N	1	Generate N variations (1-8, acemusic only)
--guidance-scale	7.0	Prompt adherence (1.0-15.0)
--infer-method	ode	ode (deterministic) or sde (stochastic, more variety)
--seed	random	Lock randomness for reproducibility

Technical Details

• acemusic cloud: XL Turbo 4B DiT + 4B LM, best quality, ~5-15s per generation
• Modal: XL Turbo 4B DiT (ACE-Step-1.5 v0.1.8), no LM, 8 steps at shift 3.0 (upstream's turbo recommendation; override with shift in the request), DCW sampler on. ~4s warm for 10s of audio, ~50s cold
• RunPod: Standard Turbo 2B DiT, no LM, ~2-3s per generation
• Output: 48kHz MP3/WAV/FLAC
• Duration range: 10-600 seconds
• BPM range: 30-300

When NOT to use ACE-Step

• Voice cloning — use Qwen3-TTS or ElevenLabs instead
• Sound effects — use ElevenLabs SFX (tools/sfx.py)
• Speech/narration — use voiceover tools, not music gen
• Stem extraction from video — extract audio first with FFmpeg, then use --extract