Voice conversion allows you to transform existing audio recordings by applying a different voice to them. Using [Octave](/content/blog/octave-the-first-text-to-speech-model-that-understands-what-its-saying/index.html), Hume’s speech-language model, you can convert any speech audio to sound like it was spoken by a voice from the [Voice Library](https://app.hume.ai/voices) or one of your custom voices, while preserving the original speech patterns, timing, and emotional expression.

Use the voice conversion playground to preview how your audio will sound with different voices:

[Voice Conversion Playground](https://app.hume.ai/voice-conversion)

## Using the voice conversion API

The voice conversion API accepts an audio file and a target voice, then returns the converted audio with the specified voice applied. You can use any voice from the Voice Library or your custom voices.

### Audio file requirements

When uploading audio files for voice conversion, follow these guidelines:

- **Format**: Supported formats include `MP3`, `WAV`, `M4A`, and `OGG`
- **Duration**: Audio files should be at least 12 seconds long and less than 3 minutes in duration
- **Quality**: For best results, use clear audio with minimal background noise
- **Content**: Input audio should contain human speech
- **Sample rate**: 44.1kHz is recommended

**Upload only audio files for which you have the necessary rights or consent to convert.** Users must comply with Hume’s [Terms of Use](/content/terms-of-use/index.html), [Ethical Guidelines](https://thehumeinitiative.org/guidelines/), [Privacy Policy](/content/privacy-policy/index.html), and applicable laws.

### Specifying a target voice

You can specify the target voice by `name` or `id`. When using `name`, include a `provider` to indicate whether you’re using a voice from the Voice Library (`HUME_AI`) or a custom voice (`CUSTOM_VOICE`).

###### By ID

###### By Name

Specify either a custom voice or one from Hume's Voice Library by ID

```json
{
  "voice": {
    "id": "f898a92e-685f-43fa-985b-a46920f0650b",
    "provider": "HUME_AI"
  }
}
```

Get voice IDs and names from [/v0/tts/voices](https://dev.hume.ai/reference/voices/list) or from the Platform’s [Voice Library page](https://app.hume.ai/voices).

## Converting audio

The following examples demonstrate how to convert an audio file using the voice conversion API. The endpoint accepts a multipart form request with the audio file and voice specification.

### cURL Example

```bash
curl --location 'https://api.hume.ai/v0/tts/voice_conversion/file' \
  -H "X-Hume-Api-Key: YOUR_HUME_API_KEY" \
  --output hume-voice-conversion-response.wav \
  -F 'audio=@path/to/your/audio.wav' \
  -F 'voice[name]=Inspiring Man' \
  -F 'voice[provider]=HUME_AI'
```

### Response format

The voice conversion API returns the converted audio file in the same format as the input, or in a format you specify. The response includes the audio data that you can save to a file or stream directly to your application.

## Best practices

- **Use clear audio**: Voice conversion works best with high-quality audio recordings that have minimal background noise and clear speech
- **Test with short clips first**: Start with shorter audio files (12-30 seconds) to verify the conversion quality before processing longer files

## Use cases

Voice conversion is useful for a variety of applications:

- **Vocal instruction**: Instead of giving the model written instruction, you can just pronounce the sentence exactly as it needs to be said
- **Voice consistency**: Standardize audio recordings to use a consistent voice across different speakers
- **Creative projects**: Experiment with different voices for audio content, podcasts, or narration

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