hermes-agent/website/docs/user-guide/features/tts.md

---
sidebar_position: 9
title: "Voice & TTS"
description: "Text-to-speech and voice message transcription across all platforms"
---

# Voice & TTS

Hermes Agent supports both text-to-speech output and voice message transcription across all messaging platforms.

## Text-to-Speech

Convert text to speech with four providers:

| Provider | Quality | Cost | API Key |
|----------|---------|------|---------|
| **Edge TTS** (default) | Good | Free | None needed |
| **ElevenLabs** | Excellent | Paid | `ELEVENLABS_API_KEY` |
| **OpenAI TTS** | Good | Paid | `VOICE_TOOLS_OPENAI_KEY` |
| **NeuTTS** | Good | Free | None needed |

### Platform Delivery

| Platform | Delivery | Format |
|----------|----------|--------|
| Telegram | Voice bubble (plays inline) | Opus `.ogg` |
| Discord | Voice bubble (Opus/OGG), falls back to file attachment | Opus/MP3 |
| WhatsApp | Audio file attachment | MP3 |
| CLI | Saved to `~/.hermes/audio_cache/` | MP3 |

### Configuration

```yaml
# In ~/.hermes/config.yaml
tts:
  provider: "edge"              # "edge" | "elevenlabs" | "openai" | "neutts"
  edge:
    voice: "en-US-AriaNeural"   # 322 voices, 74 languages
  elevenlabs:
    voice_id: "pNInz6obpgDQGcFmaJgB"  # Adam
    model_id: "eleven_multilingual_v2"
  openai:
    model: "gpt-4o-mini-tts"
    voice: "alloy"              # alloy, echo, fable, onyx, nova, shimmer
    base_url: "https://api.openai.com/v1"  # Override for OpenAI-compatible TTS endpoints
  neutts:
    ref_audio: ''
    ref_text: ''
    model: neuphonic/neutts-air-q4-gguf
    device: cpu
```

### Telegram Voice Bubbles & ffmpeg

Telegram voice bubbles require Opus/OGG audio format:

- **OpenAI and ElevenLabs** produce Opus natively — no extra setup
- **Edge TTS** (default) outputs MP3 and needs **ffmpeg** to convert:
- **NeuTTS** outputs WAV and also needs **ffmpeg** to convert for Telegram voice bubbles

```bash
# Ubuntu/Debian
sudo apt install ffmpeg

# macOS
brew install ffmpeg

# Fedora
sudo dnf install ffmpeg
```

Without ffmpeg, Edge TTS and NeuTTS audio are sent as regular audio files (playable, but shown as a rectangular player instead of a voice bubble).

:::tip
If you want voice bubbles without installing ffmpeg, switch to the OpenAI or ElevenLabs provider.
:::

## Voice Message Transcription (STT)

Voice messages sent on Telegram, Discord, WhatsApp, Slack, or Signal are automatically transcribed and injected as text into the conversation. The agent sees the transcript as normal text.

| Provider | Quality | Cost | API Key |
|----------|---------|------|---------| 
| **Local Whisper** (default) | Good | Free | None needed |
| **Groq Whisper API** | Good–Best | Free tier | `GROQ_API_KEY` |
| **OpenAI Whisper API** | Good–Best | Paid | `VOICE_TOOLS_OPENAI_KEY` or `OPENAI_API_KEY` |

:::info Zero Config
Local transcription works out of the box when `faster-whisper` is installed. If that's unavailable, Hermes can also use a local `whisper` CLI from common install locations (like `/opt/homebrew/bin`) or a custom command via `HERMES_LOCAL_STT_COMMAND`.
:::

### Configuration

```yaml
# In ~/.hermes/config.yaml
stt:
  provider: "local"           # "local" | "groq" | "openai"
  local:
    model: "base"             # tiny, base, small, medium, large-v3
  openai:
    model: "whisper-1"        # whisper-1, gpt-4o-mini-transcribe, gpt-4o-transcribe
```

### Provider Details

**Local (faster-whisper)** — Runs Whisper locally via [faster-whisper](https://github.com/SYSTRAN/faster-whisper). Uses CPU by default, GPU if available. Model sizes:

| Model | Size | Speed | Quality |
|-------|------|-------|---------|
| `tiny` | ~75 MB | Fastest | Basic |
| `base` | ~150 MB | Fast | Good (default) |
| `small` | ~500 MB | Medium | Better |
| `medium` | ~1.5 GB | Slower | Great |
| `large-v3` | ~3 GB | Slowest | Best |

**Groq API** — Requires `GROQ_API_KEY`. Good cloud fallback when you want a free hosted STT option.

**OpenAI API** — Accepts `VOICE_TOOLS_OPENAI_KEY` first and falls back to `OPENAI_API_KEY`. Supports `whisper-1`, `gpt-4o-mini-transcribe`, and `gpt-4o-transcribe`.

**Custom local CLI fallback** — Set `HERMES_LOCAL_STT_COMMAND` if you want Hermes to call a local transcription command directly. The command template supports `{input_path}`, `{output_dir}`, `{language}`, and `{model}` placeholders.

### Fallback Behavior

If your configured provider isn't available, Hermes automatically falls back:
- **Local faster-whisper unavailable** → Tries a local `whisper` CLI or `HERMES_LOCAL_STT_COMMAND` before cloud providers
- **Groq key not set** → Falls back to local transcription, then OpenAI
- **OpenAI key not set** → Falls back to local transcription, then Groq
- **Nothing available** → Voice messages pass through with an accurate note to the user