There's nothing remarkable about it. All one has to do is hit the right keys at the right time and the instrument plays itself.

Set the time after which the current quote is refreshed. Use a tool like Plash (MacOS) to set this page to your desktop's background. Tap the image to toggle unnecessary interface elements.

To load the site with the interface not showing, and with a certain refresh rate, set querystring parameters like so: https://andiquote.org/?showInterface=0&refreshDuration=300.