Stable Audio 2.5 on Sume: a 190 s track costs the same as a 5 s one

Stable Audio 2.5 is a Music Router model on Sume with the id stable-audio-2.5. It takes duration_seconds from 5 to 190 (default 60) and charges one flat price per track, so a 190-second track costs the same as a 5-second one. Pick the length the edit needs, not the shortest one you can get away with.

Sume's side is the Music Router docs, read 2026-10-14. Fal, which serves the model, lists it at $0.2 per audio generation on its Stable Audio 2.5 page, read 2026-10-14, and says it makes music and sound effects with commercial use permitted. The model returns WAV on fal.

What the router accepts

Numbers below come from the Music Router docs and the Sume pricing code on main, read 2026-10-14.

What a track costs

Fal lists $0.20 per generation and Sume sells at list times 1.25, which makes $0.25 per track whatever the length. The live number is in the credits on GET /v1/music-router/models and on the API rate card.

Ask for 190 s, trim in the edit

Because the price does not move with length, the cheap move is to request the longest bed you might use and cut it in your editor or Sume's Timeline. Compare ACE-Step, which bills per second, and CassetteAI Music, which bills per started minute: on those a long request costs more. Rows that do not list duration_seconds refuse it, as covered in which four models take it.

Put exclusions in the positive prompt. Sume does not support a non-empty negative_prompt.

curl -X POST https://api.sume.com/v1/music-router/generate \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "stable-audio-2.5",
    "prompt": "Warm ambient synth bed, 70 BPM, soft pads, no drums, no vocals, slow evolving texture, loopable",
    "duration_seconds": 190
  }'

Then fetch the audio

The call returns a job. Poll GET /v1/jobs/{id}/status, then read GET /v1/jobs/{id}/result and take the artifact whose type is audio. job.request.routed_model names the engine that ran.