There is a tiny button on the bottom of the battery box. Black, small, easy to miss. It is the Comm Priority button. The headset is designed to lower the volume of your music for a few seconds when a radio transmission is received. It will also lower the volume of phone calls. Your intercom sidetone (you can hear your own voice) also lowers the volume of music and calls.

Press that button and it will stop Com Priority.

The easiest way to figure it out is to play some music and talk into the mic and play with the button. You'll figure it out. Took me a bit.

It is all in the user manual.