Paul Garay has released a detailed review of GarageBand's DSP effects in
GarageBand 202: DSP Filter Factory.
In this new tutorial by Paul Garay, you'll See & Hear all of GarageBand's main DSP plugins in action. Along the way, you'll learn important tips & tricks about dynamic range compression, using EQs, adding phase and flange effects, reverbs, delay and much, much more.