Lexus LS600hL Owner's Manual page 533

The sound quality level is adjusted individually
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The treble, mid and bass levels can be adjusted for the each audio mode separately.
About Automatic Sound Levelizer (ASL)
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ASL automatically adjusts the volume and tone quality according to the vehicle
speed, wind noise or other noise.
LS600hL_U(OM50D26U)
5-4. Using the audio system
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