title: iPhone audio Filter
body: <p>I am considering an app which takes sound (eventually an audio track) and applies an audio filter to it.</p>
  
  <p>So I can play sounds with AudioServicesPlaySystemSound via AudioToolbox framework just fine. </p>
  
  <p>What I need is a very simple example of how I might take a sound and apply (for instance) midrange boost etc. Actually the kind of alteration is irrelevant -- if I can get my head around how the alteration is done I can figure out the rest. I am just finding both docs and examples of altering audio in code to be very scarce. </p>
  
  <p>Thanks for any help!</p>