Lyria 3.5 section markers: how to write [0:00 - 0:10] Intro prompts

Write section markers in the prompt as a timestamp range followed by a label, such as [0:00 - 0:10] Intro:, then a description of that section. Google's Gemini docs show this form for Lyria 3.5 and say to write the prompt in the language of the lyrics. Sume's Music Router docs show the same idea with markers like [0:00-0:30] Intro:.

Marker pattern

A full brief

Sume's docs recommend seven axes: emotion, genre, tempo in BPM, key, instruments, arc and era. Fold the sections into the arc.

curl -X POST https://api.sume.com/v1/music-router/generate \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: sections-001" \
  -d '{
    "model": "sume/music-auto",
    "prompt": "Hopeful synth-pop, 108 BPM, F major, modern. [0:00-0:15] Intro: warm pad and soft kick. [0:15-0:45] Verse: bass and light drums. [0:45-1:15] Chorus: full synths, lifted arc. [1:15-1:30] Outro: pad alone. Instrumental."
  }'

Rules to remember

• Sume has no duration field; a duration or duration_seconds field is rejected.
• A non-empty negative_prompt returns 400 negative_prompt_unsupported.
• Prompt length is 1 to 5,000 characters.
• Provider-reported BPM in result.lyrics is a claim, not a measurement.

Cost

Each call is $0.125 on the router. Iterating three times on a section brief is $0.375.