Music fade in


I have implemented a movement sensor which switches on my radio with some lounge music whenever somebody walks by. Works perfect but it is a bit shocking when the radio starts all of a sudden very loud.
My idea is to fade in the music so that the volume starts very low and then increases within a couple of seconds. Any idea how to implement this (or is there even an out-of-the box function?)

Radio set up is from the demo config.

Thanks for any hint!

Here’s a discussion that might give you some ideas. It’s discussing slowly dimming lights, but the same principles should apply to slowly raising the volume of a sound device.