The muting is supposed to be automatic. My E60 has this function but not the X1. I know how to adjust the guidance's volume, it's the self-muting of the music that I can't find.

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MY05 545i SMG, sport-pack, L7, comfort seats, Navigation, Auburn Dakota leather/Jet Black. Euro-delivery.[COLOR=Navy]
1998 318Ti M-Pack Hellrot Red, 5 Speed.
2013 Jet Black X1 ED October pick up.