Twilio Voice` allows developers to play audio files over phone calls, enabling interactive and immersive experiences. By using the `Node.js Twilio library`, developers can create web apps that respond to incoming HTTP requests with `TwiML` instructions, playing audio files or controlling the caller's experience. The example project uses `Express` and `ES6` features to build a server that generates `TwiML` responses to play a song over the phone, utilizing `ngrok` to expose the server to the Internet. Additionally, developers can use the `Twilio REST API` to initiate phone calls using the generated `TwiML`. This enables the creation of interactive and engaging applications with voice capabilities.