GMC 2007 Sierra 1500 Pickup Owner's Manual page 293

Setting the Tone (Bass/Treble)
AUDIO: To adjust bass or treble, press and
release AUDIO until BAS (bass) or TRE (treble)
appears on the display. Then press and hold
the up or the down arrow to increase or to
decrease. If a station is weak or has static,
decrease the treble.
To adjust bass or treble to the middle position,
select BAS or TRE. Then press and hold AUDIO
for more than two seconds until you hear a
beep. B (balance) and a zero or T (treble) and a
zero appears on the display.
To adjust both tone controls and both speaker
controls to the middle position, first end out of audio
mode by pressing another button, causing the radio
to perform that function or wait five seconds for the
display to return to time of day. Then press and hold
AUDIO for more than two seconds until you hear a
beep. CEN (center) appears on the display.
Adjusting the Speakers (Balance/Fade)
AUDIO: To adjust the balance between the right
and the left speakers, press and release AUDIO
until BAL (balance) appears on the display. Then
press and hold the up or the down arrow to move
the sound toward the right or the left speakers.
To adjust the fade between the front and the rear
speakers, press and release AUDIO until FAD
(fade) appears on the display. Then press and hold
the up or the down arrow to move the sound toward
the front or the rear speakers.
To adjust balance or fade to the middle position,
select BAL or FAD. Then press and hold AUDIO for
more than two seconds until you hear a beep.
B (balance) and a zero or F (fade) and a zero
appears on the display.
To adjust both tone controls and both speaker
controls to the middle position, first end out of audio
mode by pressing another button, causing the radio
to perform that function or wait five seconds for the
display to return to time of day. Then press and hold
AUDIO for more than two seconds until you hear a
beep. CEN (center) appears on the display.
Fade may not be available if the vehicle is a regular
cab model.
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