For the auto volume setting: Hold the button with the musical note emblem for 3 seconds. Then you can adjust the sensitivity of the auto adjusting volume with the buttons to the left and right of the "note" button. It will show on the radio's display. I think the settings are from 1-6 with 1 being the lowest.

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'05 X3 3.0i Alpine White/Gray Leather/Alum. Trim
Sport/Steptronic/Servotronic/Panoramic
Prem. Sound/Staggered 18" Style 114 Y-Spokes