A little over a year ago I wrote MIUI 12 gets a Windows-style sound mixer, which I thought was simply out of the repertoire in the end, but it turns out it's not, it just needs to be authorised.
The familiar sound mixer from Windows, but you don't necessarily need a computer to use it.
In the preferences, select the Sounds and vibrations menu, and within that, select the Sound assistant function.
The second option "Enable multiple voices" must be activated. Then one of the played sounds will no longer be silenced if you start another one, and the music will not be paused for several seconds if you play music via Bluetooth and receive a Messenger message.
The sound mixer can be accessed by clicking on a small note icon on the left when you adjust the volume, and then pressing on it to use the sound mixer.
