Connecting an i-pod nano to a stereo.

When I connect my 4th gen I-pod nano to my stereo via usb cable it plays like a charm only one problem.

For some reason, I cannot get the I-pod to play the music I choose nor do the manual controls of the I-Pod work

when the usb is connected. It just plays what music it wants regardless of the playlist or music i program it to play.

Any suggestions?