Text-to-Speech (Json) | Hume API

Authentication

X-Hume-Api-Keystring

API Key authentication via header

Request

This endpoint expects an object.

utterances list of objects Required

A list of Utterances to be converted to speech output.

An Utterance is a unit of input for Octave, and includes input text, an optional description to serve as the prompt for how the speech should be delivered, an optional voice specification, and additional controls to guide delivery for speed and trailing_silence.

context object or null Optional

Utterances to use as context for generating consistent speech style and prosody across multiple requests. These will not be converted to speech output.

format object Optional Defaults to {"type":"mp3"}

Specifies the output audio file format.

include_timestamp_types list of enums Optional Defaults to []

The set of timestamp types to include in the response. Only supported for Octave 2 requests.

Allowed values: word, phoneme

num_generations integer Optional 1-5 Defaults to 1

Number of audio generations to produce from the input utterances.

Using num_generations enables faster processing than issuing multiple sequential requests. Additionally, specifying num_generations allows prosody continuation across all generations without repeating context, ensuring each generation sounds slightly different while maintaining contextual consistency.

split_utterances boolean Optional Defaults to true

Controls how audio output is segmented in the response.

This setting affects how the snippets array is structured in the response, which may be important for applications that need to track the relationship between input text and generated audio segments. When setting to false, avoid including utterances with long text, as this can result in distorted output.

strip_headers boolean Optional Defaults to false

If enabled, the audio for all the chunks of a generation, once concatenated together, will constitute a single audio file. Otherwise, if disabled, each chunk’s audio will be its own audio file, each with its own headers (if applicable).

temperature double or null Optional 0.1-1

Sampling temperature for the speech generation model. Higher values increase variation; lower values increase consistency.

This is an experimental parameter. It is recommended to use the default values for most use cases.

Defaults when omitted:

version enum Optional

Selects the Octave model version used to synthesize speech for this request. If you omit this field, Hume automatically routes the request to the most appropriate model. Setting a specific version ensures stable and repeatable behavior across requests.

Use 2 to opt into the latest Octave capabilities. When you specify version 2, you must also provide a voice. Requests that set version: 2 without a voice will be rejected.

Allowed values: 1, 2

instant_mode boolean Optional Defaults to true

Enables ultra-low latency streaming, significantly reducing the time until the first audio chunk is received. Recommended for real-time applications requiring immediate audio playback. For further details, see our documentation on instant mode.