This third part of the book concerns signal processing, which is the input of a real audio signal and using it to produce something else. Conventional wisdom will say that you can’t do much in the way of signal processing with a simple Arduino Uno, but you can do quite a lot more than you might think. By extending your processor to a Due or Teensy 3, you can do quite a bit more. So lets start off with the theory before jumping into some fun projects. Note that this is not going to be an audiophile examination of the subject, but an engineering one. That means I am not concerned with anything you can’t measure with an instrument. The point of view that “the ear can pick up things that instruments can’t measure” is the mumbo jumbo homeopathy approach to audio that has you buying expensive gold plated mains connectors and precious metal digital leads.