A voice is the hardest part of a config to get right, because for most providers it is not checked when you save the project. The API knows each provider’s fields, not its whole catalogue: a voice that does not exist, or does not speak the language, is found out only when a file is processed. Then the file fails, or sounds wrong. What is checked on save: a Deepdub voice must be auto, and a MultiVoice dub needs a language that has MultiVoice voices; anything else answers 422. For Amazon Polly, Azure and Google, GET /voices lists known voices for a language.

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Start here

Each of these ran end to end on build 0.9.0-alpha1-2026-09-28T12-19Z-118f0e, in the language shown: Sarvam ({"@type": "Sarvam"}) clones voices for Indian languages and takes no voice.
With several speakers, cloning (Deepdub, Sarvam) gives each speaker a voice of their own. A catalogue voice gives everyone the same one, which suits narration and single presenters. {"@type": "MultiVoice"} gives each speaker a different catalogue voice, chosen for you from SyncWords’ voices for the language: see Dubbing.

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Known voices

GET /voices lists the Amazon Polly, Azure and Google voices SyncWords knows for a language, in every dialect of it (es gives Spain’s, Mexico’s and the others’), plus the Azure voices that speak many languages:
Put voice in provider.voice, and for Amazon one of engines in provider.engine. A voice with multilingual: true speaks many languages; the provider’s list says which.
The list is not each provider’s whole catalogue, and it is not a check: a voice missing from it is still accepted. Google’s newer voices (Chirp, Studio) are not in it, nor is every Standard voice: es-ES-Standard-A from the table above works and is not listed. For those, use the provider’s own list below.

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Finding other voices

The voice must speak the translation’s language: an Azure, Google or Polly name carries its locale (es-ES-…), and a multilingual voice speaks many. For Polly, not every voice has every engine: check the list’s engine columns.

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Try a voice before a whole season

  1. Create a project with the voice and options.autoStart: false.
  2. Upload one short clip: a minute is enough, and the sample video works.
  3. Start the project, wait for the file, and listen.
  4. A failed file with a voice you just changed usually means the voice is wrong: a file with lines the voice could not say fails.
  5. Once it sounds right, upload the rest, or PATCH the same config into the real project.

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Pronunciation

For names and brands a voice says wrongly, ttsOptions.dictionary maps a word to how it is spoken ({"Newsmax": "news max"}), and ttsOptions.locale picks the accent of the language (es-XL, Latin American Spanish). See Dubbing.