Wait, hang on.... I'll bet Mark could implement an actual bass/treble slider in Hijack. I'll bet there's enough information visible in the kernel and in the DSP spec sheet for Mark to figure out how to directly manipulate the DSP's bass and treble controls.

And he's already hijacked the button press, so...

Calling Mark Lord, are you reading this thread?

And while you're playing with this, you can implement my configurable loudness cutoff.