Bluetooth and line input with microphone passthrough

I ride a motorcycle and currently have a cardo pack talk slim. I am looking to buy a new helmet and don't want to transplant the electronics so I am brainstorming something that stays on my person and doesn't attach to the helmet.

My idea was to have a two-way radio as a form of communication with other riders, but a Bluetooth accessory to connect to my phone for music.

This presents an interesting problem to solve since both inputs need to reach the headphones, but the two-way radio input needs to take priority for communication.

I would like to build a circuit that will take both inputs and pass them to a single output (headphones) but lower the volume of input 2 (bluetooth music) when input is received from input 1 (two-way radio)

I understand this may sound impractical, but it's more about learning about electrical components and circuits than anything. It's also a concept I would like to put to the test since the same circuit could be used for say a music speaker that doubles as a PA system by swapping the Bluetooth module for something that acts as wifi speaker.

Any and all help is appreciated as I have never touched anything like this and am very anxious to learn!