Sound glitches out and menu music missing

I have experienced this too. Though I noticed that it was always with one specific sound. E.g. in one match suddenly all the Lewis guns on the map made a diferrently pitched sound, which was audible over longer distances. In another match is was another weapon, though I did not see which one, but I could hear it clearly over the distance. I´ll try to get a video sample next time.

Sound: 7.1  with War Tapes