ACE-Step Songwriting Guide

Professional music creation knowledge for writing captions, lyrics, and choosing music parameters for ACE-Step.

Output Format

After using this guide, produce two things for the acestep skill:

1. Caption (-c): Style/genre/instruments/emotion description
2. Lyrics (-l): Complete structured lyrics with tags
3. Parameters: --duration, --bpm, --key, --time-signature, --language

Caption: The Most Important Input

Caption is the most important factor affecting generated music.

Supports multiple formats: simple style words, comma-separated tags, complex natural language descriptions.

Common Dimensions

Caption Writing Principles

1. Specific beats vague — "sad piano ballad with female breathy vocal" > "a sad song"
2. Combine multiple dimensions — style+emotion+instruments+timbre anchors direction precisely
3. Use references well — "in the style of 80s synthwave" conveys complex aesthetic quickly
4. Texture words are useful — warm, crisp, airy, punchy influence mixing and timbre
5. Don't pursue perfection — Caption is a starting point, iterate based on results
6. Granularity determines freedom — Less detail = more model creativity; more detail = more control
7. Avoid conflicting words — "classical strings" + "hardcore metal" degrades output
   • Fix: Repetition reinforcement — Repeat the elements you want more
   • Fix: Conflict to evolution — "Start with soft strings, middle becomes metal rock, end turns to hip-hop"
8. Don't put BPM/key/tempo in Caption — Use dedicated parameters instead

Lyrics: The Temporal Script

Lyrics controls how music unfolds over time. It carries:

• Lyric text itself
• Structure tags ([Verse], [Chorus], [Bridge]...)
• Vocal style hints ([raspy vocal], [whispered]...)
• Instrumental sections ([guitar solo], [drum break]...)
• Energy changes ([building energy], [explosive drop]...)

Structure Tags

Combining Tags

Use - for finer control, but keep it concise:

✅ [Chorus - anthemic]
❌ [Chorus - anthemic - stacked harmonies - high energy - powerful - epic]

Put complex style descriptions in Caption, not in tags.

Caption-Lyrics Consistency

Models are not good at resolving conflicts. Checklist:

• Instruments in Caption ↔ Instrumental section tags in Lyrics
• Emotion in Caption ↔ Energy tags in Lyrics
• Vocal description in Caption ↔ Vocal control tags in Lyrics

Vocal Control Tags

Energy and Emotion Tags

Lyric Writing Tips

1. 6-10 syllables per line — Model aligns syllables to beats; keep similar counts for lines in same position (±1-2)
2. Uppercase = stronger intensity — WE ARE THE CHAMPIONS! (shouting) vs walking through the streets (normal)
3. Parentheses = background vocals — We rise together (together)
4. Extend vowels — Feeeling so aliiive (use cautiously, effects unstable)
5. Clear section separation — Blank lines between sections

Avoiding "AI-flavored" Lyrics

Metaphor discipline: One core metaphor per song, explore its multiple aspects.

Music Metadata

Most of the time, let LM auto-infer. Only set manually when you have clear requirements.

When to Set Manually

Duration Calculation

Estimation Method

• Intro/Outro: 5-10 seconds each
• Instrumental sections: 5-15 seconds each
• Typical structures:
  • 2 verses + 2 choruses: 120-150s minimum
  • 2 verses + 2 choruses + bridge: 180-240s minimum
  • Full song with intro/outro: 210-270s (3.5-4.5 min)

BPM and Duration Relationship

• Slower BPM (60-80): Need MORE duration for same lyrics
• Medium BPM (100-130): Standard duration
• Faster BPM (150-180): Can fit more lyrics, but still need breathing room

Rule of thumb: When in doubt, estimate longer. A song too short feels rushed.

Note: Lyrics tags (piano, powerful, whispered) are consistent with Caption (piano ballad, building to powerful chorus, intimate).