Set a Lyria track's length on Sume: duration is rejected

Write the length into the prompt. The Sume Music Router rejects both duration and duration_seconds, and tells you to steer length in the prompt with phrases like a 2-minute track or time-coded sections such as [0:00-0:30] Intro. The route that serves Lyria 3.5 today is POST /v1/music-router/generate.

What the prompt can carry

• 1 to 5000 characters.
• Plain length: A 30-second track.
• Sections: [0:00-0:10] Intro: soft pad, then [0:10-0:30] Drop: brushed drums.
• Exclusions go in the positive prompt. A non-empty negative_prompt is unsupported, so omit it or send an empty string.
• Instrumental only: say so in the words, for example Instrumental, no vocals.

Cost

Every Music Router model charges the fixed Music price per audio generation: $0.125 per accepted job, regardless of prompt length or optional image conditioning (see Music 1.0). A client brief that tries five 30-second moods is 5 x $0.125 = $0.625. The track length is not a price lever.

Matching a Short

For a 45-second vertical, ask for 45 seconds and plan to check the returned audio duration. The docs do not promise sample-exact length, so trim afterward with Timeline audio or let the render cut it. A reference still can steer mood: image_url takes a public HTTPS image.

Request

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: music-45s-001" \
  -d '{"model":"sume/music-auto","prompt":"[0:00-0:10] Intro: soft pad. [0:10-0:45] Groove: warm lo-fi drums, 84 BPM. A 45-second track. Instrumental, no vocals."}'