This code is very old and no longer maintained. It may work, it may not but I've no intention of updating it any time soon!
Audio file sourced from http://www.freesound.org/people/Corsica_S/sounds/75064/
Demonstration of mixing between two effects using AVFoundation on iOS. Please see my blog post at http://www.robotlovesyou.com/mixing-between-effects-with-avfoundation for details.