kyleneideck/BackgroundMusic ? reverse-engineered prompt

Build me a macOS app that sits in the background and manages system audio the way Background Music does.

I want it to automatically pause my music player when another app starts playing sound, then resume it when that other audio stops. It should also let me control the volume of each app separately, including boosting quieter apps above their normal max if needed. On top of that, I want it to act like a virtual audio device so I can record system audio in apps like QuickTime, and optionally combine that with my microphone using an aggregate device.

Make it feel like a simple utility with a small settings window and a clear volume slider for running apps. It should start up cleanly, switch the system output when needed, and restore things when I quit. If you need to check current macOS docs or APIs while building it, go ahead and look them up online.