(Book). Progressive Drumming Essentials is a collection of material originally written for Modern Drummer magazine plus extensive additional content. This book breaks down fun and challenging material for progressive-minded drummers, including double bass, odd time signatures, displacements, odd subdivisions, and modulations, plus an in-depth section on polyrhythms and their applications to the drumset. Author Aaron Edgar is the drummer for the prog-metal band Third Ion. He's a regular instructor on Drumeo.com and a regular columnist for Modern Drummer magazine. He is known for teaching advanced rhythmic concepts and has a knack for being able to break down and explain challenging material in an easily understandable way.