Audio Systems: 2005 Yukon XL Denali - Audio System, yukon xl denali, external audio sources

Question
I recently purchased a 2005 Yukon XL Denali with a 6-disc changer and a rear audio system. My children cannot access CDs in the changer when I am listening to XM radio. (They can listen to the CD in the main stereo, and to XM or regular radio channels, just not the changer.)

Also, when I turn on the ignition, you can hear the changer cycle through all the CDs. My brother-in-law owns two '05 Yukons, and says that his do not do this. I'm wondering whether I need to have the stereo serviced before the car is out of warranty.

Answer
external cd changer and external xm are external audio sources not part of the radio  both of them are not inside the radio

you can only play one external source at the time ,if you are listening to xm the only options are the cd in the radio and the am/fm tuner