ElevenLabs music API: composition plans vs a prompt-only API
ElevenLabs added Music v2.5 API support on 2026-09-14 with composition plans. How a plan differs from Sume's prompt-only music route with no duration field
The ElevenLabs music API gained Music v2.5 support on 2026-09-14, and its changelog mentions composition plans with capacity up to 6,132 characters. Sume's music route works differently: it is prompt-only, with no duration parameter, so structure and length go inside the prompt text. Sume does not list ElevenLabs music in its Music Router, so this is a comparison of request shapes, not a switch.
What did ElevenLabs add?
Per its changelog, read 2026-09-29: Music v2.5 API support, and composition plan capacity up to 6,132 characters. Its Music v2.5 page says the model is available in ElevenMusic, ElevenCreative and the ElevenLabs API. This post does not describe the plan format beyond those pages; read ElevenLabs' API reference for fields.
How does Sume's prompt-only request differ?
On POST /v1/music-router/generate you send a prompt of 1 to 5000 characters and optionally an image_url. The docs state there is no seed, temperature, guidance or duration parameter and that duration and duration_seconds are rejected. You steer length and structure in the prompt, for example with section markers like [0:00-0:30] Intro: ....
| Item | ElevenLabs (changelog) | Sume (docs) |
|---|---|---|
| Structure input | Composition plans, up to 6,132 characters | Section markers inside the prompt |
| Prompt limit | See ElevenLabs API reference | 1 to 5000 characters |
| Duration field | See ElevenLabs API reference | Rejected |
| Music v2.5 access | Available in the API | Not listed in the Music Router |
Which shape fits my project?
If you want a machine-written structure you can edit and resend, a plan-style API is the shape to study at ElevenLabs. If you want one text brief that a person can rewrite, Sume's route fits, and its engines are sume/music-auto, lyria-3.5 and lyria-3-pro. Length control on Sume is a request in words, so verify the result. See Lyria 3.5 song length for what to expect.
How do I write structure into a Sume prompt?
Use section markers and one named moment. The docs' own example says the trumpet answers the Rhodes from 0:12 and the bass thickens for the last pass, and their marker form is [0:00-0:30] Intro: .... That gives a text brief with timed sections, though the docs stress these are directions rather than guaranteed settings, so check the audio.
What is the short version?
ElevenLabs added Music v2.5 API support with composition plans on 2026-09-14. Sume's music route is prompt-only, with no duration field and a 5000 character prompt. If your project needs a structured plan object, study ElevenLabs' API reference; if a text brief with timed sections is enough, Sume's route fits.
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