In this final article of a four-part series discussing how computer-based music synthesis works and presenting a basic platform for experimentation, I'll discuss effects. An effect is a general term for a class of component that manipulates samples towards some particular end. Example effects include tremelo, phaser, flanger, reverb, delay, equalizer, pitch shifter, chorus, compressor, expander, limiter, etc. This article will describe how to implement a delay and a phaser effect using the architecture developed over the course of this series.