Speaking of set up of Apple devices: treble and bass adjustments?

[August West]

I’m looking for something that can alter output dynamically in real time*.

I'm not quite sure how any dynamic adjustments to the treble and bass levels of an iPhone’s sound output will be done without post-processing As far as I can tell you are in need of a method to insert a dynamic eq or multiband compressor before final output. Perhaps I'm just not understanding your problem.