Skip to main content
Your agent speaks with a voice model from the Fish Audio Voice Library: the same voices you use for text to speech. Pick one in the Builder, or set it through the API, and choose the language the agent holds conversations in.

Configuration page

Where the voice and language settings live in the Builder.

Voice Library

Browse public voices and manage your own.

Voice Cloning

Create a custom voice, then use it here. See Voice Cloning.

​
Pick a voice in the Builder

The voice picker on the Configuration page has two levels: a curated list for a fast start, and the full Voice Library when you want something specific.
1

Open the voice selector

In your agent’s Configuration page, open the voice card. The Choose a voice view shows a curated selection of voices.
2

Browse the full library (optional)

Not seeing the right fit? Select More voices to open the Select Voice browser: the full Voice Library, with your own cloned voices under My Voices.
3

Save automatically

Your selection is written to the agent’s draft configuration as soon as you pick it. Start a preview call to hear the voice in a real conversation.
4

Publish

Draft changes don’t affect live sessions until you Publish. See Versions & publishing.

​
Use any voice model

The agent’s voice is a voice model id (voice_id): the same ids used as reference_id in Text to Speech. Any public voice model from the Voice Library works, including:
  • Library voices: Ready-made public voices. Find ids in the Voice Library.
  • Your cloned voices: Clone a voice once, then use its model id as your agent’s voice.

​
Set the voice via API

Voice settings live in the voice section of the agent’s configuration. Patches are partial: only the fields you send change, and the result is saved to the draft:
voice.speaking_language lives in the same section and is patched the same way. As in the Builder, API edits land in the draft. Publish to roll them out.

​
Speaking language

Speaking language sets the language for the agent’s conversations: one of en, ja, zh, ko, es, fr, or de (voice.speaking_language on the wire). Every session converses in this language.
The voice model and the speaking language are independent settings: picking a voice does not change the language, and vice versa. Choose a voice that sounds natural in the language you configure.
Both settings can also be replaced for a single session: send overrides.voice_id or overrides.language on the session request. See Overrides.

​
Speaking speed

Speaking speed sets how fast the agent talks, as a multiplier from 0.5 (half speed) to 2.0 (double speed). The default is 1.0. Many English-language agents sound more natural at a slightly faster rate, such as 1.2. Set it with the Speaking speed slider in the Builder’s voice section, or via the API (voice.speed, default 1.0):
The rate applies to everything the agent speaks in voice and phone sessions. As with every voice setting, the change lands in the draft: publish to roll it out.

​
Expressive mode

Expressive mode makes the agent steer its own delivery: it opens sentences with emotion cues, adds natural pauses and emphasis, laughs where it genuinely fits, and speaks the way people talk, with contractions and the occasional “um”. You get lively, emotionally aware speech without writing any delivery rules into your prompt. Turn it on with the Expressive mode switch in the Builder’s voice section, or via the API (voice.expressive, default false):
The delivery cues are rendered by the voice model. They are never spoken and never appear in transcripts or message history. Expressive mode applies to spoken sessions (voice calls and phone); text chat is unaffected.
Keep your system prompt about what the agent says: who it is, what it knows, what it should do. With expressive mode on, how it sounds is handled for you.

​
Going further

Agent configuration

System prompt, first message, and conversation settings.

System tools

Built-in capabilities like hanging up the call.

Preview calls

Talk to your draft agent and hear the voice live.

Versions & publishing

How drafts become the live agent.