> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fish.audio/llms.txt
> Use this file to discover all available pages before exploring further.

# Voice & Language

> Choose the voice your agent speaks with and the language it converses in

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.

<CardGroup cols={3}>
  <Card title="Configuration page" icon="sliders" href="/agents/build/configuration">
    Where the voice and language settings live in the Builder.
  </Card>

  <Card title="Voice Library" icon="book-open" href="/features/manage-voices">
    Browse public voices and manage your own.
  </Card>

  <Card title="Voice Cloning" icon="clone">
    Create a custom voice, then use it here. See [Voice Cloning](/features/voice-cloning).
  </Card>
</CardGroup>

## 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.

<Steps>
  <Step title="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.
  </Step>

  <Step title="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**.
  </Step>

  <Step title="Save automatically">
    Your selection is written to the agent's draft configuration as soon as you pick it — there is no Save button. Start a [preview call](/agents/test/preview-calls) to hear the voice in a real conversation.
  </Step>

  <Step title="Publish">
    Draft changes don't affect live sessions until you **Publish**. See [Versions & publishing](/agents/deploy/versions-publishing).
  </Step>
</Steps>

## 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](/features/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](/features/manage-voices).
* **Your cloned voices** — [clone a voice](/features/voice-cloning) 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:

<CodeGroup>
  ```bash API (curl) theme={null}
  curl --request PATCH "https://api.fish.audio/v1/agent/agents/$AGENT_ID/config" \
    --header "Authorization: Bearer $FISH_API_KEY" \
    --header "Content-Type: application/json" \
    --data '{
      "voice": {
        "voice_id": "802e3bc2b27e49c2995d23ef70e6ac89"
      }
    }'
  ```
</CodeGroup>

`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 default language for the agent's conversations — one of `en`, `ja`, `zh`, `ko`, `es`, `fr`, or `de` (`voice.speaking_language` on the wire). Whether it is pinned or just a fallback depends on the **Language detection** [system tool](/agents/build/system-tools):

| Language detection | Session behavior                                                                                         |
| ------------------ | -------------------------------------------------------------------------------------------------------- |
| On                 | The session runs in automatic language mode — the agent follows the language the caller actually speaks. |
| Off (default)      | Every session uses the configured speaking language.                                                     |

<Tip>
  If your agent must always converse in one specific language, leave Language detection off — the session then sticks to `speaking_language` regardless of what it hears.
</Tip>

<Note>
  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.
</Note>

Both settings can also be replaced for a single session — send `overrides.voice_id` or `overrides.language` on the session request. See [Overrides](/agents/deploy/authenticated-sessions#overrides).

## Going further

<CardGroup cols={2}>
  <Card title="Agent configuration" icon="sliders" href="/agents/build/configuration">
    System prompt, first message, and conversation settings.
  </Card>

  <Card title="System tools" icon="wrench" href="/agents/build/system-tools">
    Language detection and other built-in capabilities.
  </Card>

  <Card title="Preview calls" icon="phone" href="/agents/test/preview-calls">
    Talk to your draft agent and hear the voice live.
  </Card>

  <Card title="Versions & publishing" icon="rocket" href="/agents/deploy/versions-publishing">
    How drafts become the live agent.
  </Card>
</CardGroup>