Music Theory for Real-World Musicians. If you'd like to know about music theory but don't want to get bogged down in a stuffy college-level textbook, this guide was written just for you! It's a practical, no-nonsense book ideal for: young musicians learning guitar so they can play rock, folk or blues; DJs who've started recording their own tracks and need to know how chord progressions work; anyone who wants to play from the chord symbols in sheet music; classical musicians who want to do more than just read the dots, and countless others.