Is it because everything's on one screen, or does it have to do with how the knobs were implemented? Or that every knob has an associated text label?
 
I've done some reading on accessibility issues. Slau wrote a great blog post about it. If you don't know Slau, he's an outstanding musician, engineer, producer, and microphone expert. And blind. The article is here.
 
My curiosity about this stems from my day job, which involves creating user interfaces for my own (non-music related) software. I am embarrassingly ignorant when it comes to screen readers. Here's another question for you: does font size matter, or do screen readers not care how big the text is?