2007 GMC Acadia Owner's Manual - Page 278

To use a portable audio player, connect a 3.5 mm (1/8 inch) cable to the radio's front auxiliary input jack. When a device is connected, press the radio CD/AUX button to begin playing audio from the device over the vehicle speakers. Radio with CD and DVD O (Power/Volume): Turn this knob clockwise or counterclockwise to increase or decrease the volume of the portable player. You might need to do additional volume adjustments from the portable device if the volume does not go loud or soft enough. BAND: Press this button to listen to the radio when a portable audio device is playing. The portable audio device continues playing, so you might want to stop it or turn it off. CD/AUX (CD/Auxiliary): Press this button to play a CD when a portable audio device is playing. Press this button again and the system begins playing audio from the connected portable audio player. If a portable audio player is not connected, "No input device found" displays. If your vehicle has a Rear Seat Entertainment (RSE) system, it has a CD/DVD radio. See Rear Seat Entertainment System on page 311 for more information on the vehicle's RSE system. 278