See also:

Adjusting volume
Turn knob 1next to the CD/DVD player until the desired volume is obtained. You can also adjust the volume with buttons on the steering wheel. ...

USB audio interface/mobile phone audio interface
At a glance It is possible to connect external audio devices. They can be operated via iDrive. The sound is output on the vehicle loudspeakers Connectors for external devices ▷ Connection ...

Activation/deactivation
Press the button. ...