I beg to differ.  This is an issue with the Pandora app.  If you use Apple Maps with Apple Music, everything works as expected; the Maps voice announces directions atop the reduced volume of the music; afterwards, the original volume of the music is restored.  This behavior continues for all subsequent direction announcements without any user actions required.  However, as has already been exhaustively explained, the mute button option must first be selected in Maps for the volume of the music in Pandora to be restored.  Afterwards, the spoken audio button option is again selected in Maps but the very next voice instruction breaks everything and causes the issue herein to resume. ... View more