ElevenLabs Music output_format list vs the file Sume returns

ElevenLabs Compose accepts an output_format with MP3, PCM, mu-law, A-law and Opus variants. Sume's music request has no format field: the completed job returns an audio artifact, typically audio/mpeg, and you convert to wav with a Timeline audio job.

What ElevenLabs lists

The Compose reference lists auto as the default plus MP3 at several sample rates and bitrates, PCM from 8000 to 48000 Hz, ulaw_8000, alaw_8000 and Opus at 48 kHz (read 2026-10-02). The capabilities page says output is MP3 (44.1 kHz, 128 to 192 kbps) and WAV (read 2026-10-02).

Getting wav on Sume

Timeline audio takes Sume-hosted audio and returns a durable file. Its output.format is wav by default (pcm_s16le) or mp3. A concat with one part is a valid input, since parts takes 1 to 20 items, so it works as a conversion step.

Note the docs warn that mp3 output re-adds priming padding at every edge, so keep wav for anything you will cut again.

Telephony and low-bitrate targets

Mu-law, A-law and 8 kHz PCM matter for phone systems. Sume's music docs list none of those, so for hold music you generate the track and convert it in your own pipeline. The Sume Timeline docs do not cover mu-law either.

For web delivery, an mp3 file from a Music job usually needs no conversion. Do not assume a sample rate: inspect the artifact before you hand it to a platform with strict audio specs.