From An Auxiliary Device; Control Your Music; Volume - Motorola 68014301013 User Manual

You'll see a screen like this when music begins playing
from your USB device:
John Smith
Greensleeves

From an auxiliary device

1 From the home screen, select Music > Auxiliary
Music.
2 Press the scroll knob to play music.
You will then see this screen:
Auxiliary Music

Control your music

To...
play or pause press
go to previous press
track
rewind track press and hold
24 Music
To...
go to next track press
fast-forward press and hold
track
stop, exit music press and hold
mode and return
to car stereo
Note: For music played from a Bluetooth device, when
remote control capabilities (AVRCP profile) are not
supported by your Bluetooth device, music cannot be
controlled on your car kit.
Note: For music played from a Bluetooth device supporting
remote control capabilities, the rewind track and
fast-forward track controls are not supported.
Note: Music played from an auxiliary device cannot be
controlled by your car kit.

Volume

To adjust music volume, turn the scroll knob clockwise to
increase or counterclockwise to decrease
You'll hear a tone when maximum or minimum volume is
reached on your car kit.