Toyota100: The Toyota Century Forum

The manual seems to suggest that I can do this by pressing the sound quality adjustment button, then using the right-hand up/down buttons to adjust bass or treble. However... I do seem to be able to select the three modes, but pressing the up/down buttons just skip between CD tracks like they usually do.

Any ideas? Am I misinterpreting this?

Best you can do is change between the 3 equalizer settings. One setting is flat, one setting boosts vocals, and one boosts bass & treble for listening to music. It is the button next to the "sound field" button that shows seating positions.