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

# Voices

> Choose the voice and language your calls speak, and find the right voice in a catalog of more than 2,000.

Every call speaks with a voice. Leave `voice` unset and calls use Dairo's default conversational English voice; set `language` to hold the call in another language, or pick a different voice from the catalog.

## Set the language

Calls default to English. Set `language` to an ISO code and the agent both speaks and understands that language — with the default voice or any voice you choose:

```json theme={null}
{
  "to": "+4915112345678",
  "from": "+13125550100",
  "instructions": "Erinnere Frau Weber daran, dass die Rechnung INV-2201 am Freitag fällig ist. Biete an, sie per E-Mail erneut zu senden.",
  "language": "de"
}
```

<Tip>
  The agent phrases things itself. Give `instructions` a goal, a tone, and the facts it may share rather than lines to read verbatim — a brief produces a natural conversation, a script produces a recital.
</Tip>

## Find a voice

The phone voice catalog holds more than 2,000 curated conversational voices across roughly 30 languages, genders, ages, and accents. Search it by name or by described vibe with the `search_voices` tool on Dairo's [MCP server](/agent-first/mcp-server), filtering by `language` or `gender` when it helps:

```text title="MCP" theme={null}
Tool: search_voices
Args: { "query": "warm older German woman", "kind": "phone", "language": "de", "limit": 5 }
```

Results come back ranked, and each row carries the voice's `voiceId`, `name`, `description`, `language`, `gender`, `age`, `accent`, and a `previewUrl` you can listen to before deciding. Pass the winning row's `voiceId` as the call's `voice` — together with `language` when the call isn't in English. Both fields are set per call on [Making calls](/phone/making-calls).

<Note>
  Placing the call never fails on a voice: if the voice you picked can't currently be used for calls, the call itself settles as `failed` with the reason in `error`. Pick another voice from the catalog and dial again.
</Note>

## Background audio

`backgroundAudio` selects the sound bed behind the agent's voice. Three values are accepted — `silence` (the default), `office`, and `none` — and anything else is rejected with `400`.