Demo project from Forward Swift and CocoaConf to decompress an audio file (MP3, AAC, etc) to LPCM, reverse the samples in another LPCM file, and allow forward/backward playback. Fun for use with "back-masked" messages in old rock songs ("Revolution No. 9", "Fire On High", etc.)
Point of the demo is to illustrate calling into Core Audio / Audio Toolbox from Swift and when it makes sense to write entire functions in C rather than convert Core Audio calls one-by-one to Swift.
Music files are loaded from the app's Documents directory. On a device, load these with iTunes file-sharing; on simulator, watch the console log at startup for the directory that you need to copy the files into.