GMC 2007 Sierra 1500 Pickup Owner's Manual page 326

To insert multiple CDs, do the following:
1. Turn the ignition on.
2. Press and hold the LOAD button for
two seconds.
You will hear a beep and the indicator light,
located to the right of the slot, will begin
to flash and MULTI LOAD # will appear on the
display.
3. Once the light stops flashing and turns green,
INSERT CD # will appear on the display, load
a CD. Insert the CD part way into the slot,
label side up. The player will pull the CD in.
Once the CD is loaded, the indicator light
will begin flashing again. Once the light stops
flashing and turns green, you can load
another CD. The CD player takes up to six
CDs. Do not try to load more than six.
To load more than one CD but less than six,
complete Steps 1 through 3. When finished loading
CDs, press the LOAD button to cancel the
loading function. The radio will begin to play the
last CD loaded.
If more than one CD has been loaded, a number
for each CD will appear on the display.
326
Playing a Specific Loaded CD
For every CD loaded, a number will appear on the
display. To play a specific CD, first press the
CD AUX button, then press the numbered
pushbutton that corresponds to the CD. A small
bar will appear under the CD number that is
playing and the track number will appear on the
display.
If an error appears on the display, see "CD
Messages" later in this section.
CD (Eject): Press this button to eject CD(s).
Z
To eject the CD that is currently playing, press
and release this button.
To eject multiple CDs, do the following:
1. Press and hold the CD eject button for
two seconds.
You will hear a beep and the indicator light,
located to the right of the slot, will begin
to flash and EJECT ALL will appear on the
display.
2. Once the light stops flashing, REMOVE CD #
will appear on the display. The CD will eject
and can be removed.