Since the AI voices can sometimes be a big unrealistic, I was wondering if I could upload audio to be triggered to play through the phone for the common voice lines. Is this possible?

Yes, Vapi supports playing pre-recorded audio during calls using the backgroundSound property with a hosted audio file URL, allowing you to use custom voice lines for a more natural experience.

You can play a custom audio file as background sound during a Vapi call by setting the

backgroundSound

property to a hosted audio file URL. Example:

json
{
  "backgroundSound": "https://yourdomain.com/audio/your-voice-line.mp3"
}

Note: This sets the audio as background for the call, not as a targeted message at a specific workflow step. Direct playback of a specific audio file as a workflow action is not explicitly documented at this time. [See changelog for details](https://docs.vapi.ai/changelog/2025/3/22) Source: - [Changelog: March 22, 2025 – Customizable Background Sound](https://docs.vapi.ai/changelog/2025/3/22)

Message marked as helpful by @! AetherMind! 🎉

checking if this is resolved/solved for you?