Using the tools of music theory, you can look back at any piece of music, new or old, and figure out what chords are used and why. The better question to ask is why. Why did anything happen the way it did? Why did Bach use certain chords and not others? Why did Beethoven and Mozart use similar chords? Were they working from some sort of rule book, so to speak? The answer is no. Harmony developed. It's as simple as that. Diatonic harmony was a long time in the making. It started with one voice, then a second was added, and so on, and then eventually triads and harmony fell into place. It wasn't until the baroque era that harmony started to solidify into something recognizable. This wasn't because Bach and his buddies had a handbook. The music evolved because musicians listened and studied what had come before. They took what they liked and moved forward.

Theorists look back and try to fit all the music into a set of rules. But this is not always in your best interest. It is worth noting that a certain sequence of chords happens over and over and over again, but trying to figure out why will drive you crazy.

To help you tackle this issue, this book is going to do about 300 years’ worth of homework, sorting through the massive amounts of music and arriving at some conclusions. In the end, you'll understand that there are sounds associated with feelings, moods, and other things that cannot be quantified with theory. “Amen” can be summarized by playing a IV chord followed by a I chord. Much of music can be summarized in this way, but which chord to use and when is up to you. After you've studied a few examples of some common progressions, the rest of music and composition is up to you to explore. Beyond the basic tools, there are no rules. Some of the coolest modern music breaks every rule there is, yet it sounds beautiful. Remember: music first, theory second. In this chapter, you're going to get a bunch of theory; it's up to you to turn the theory into music in the next chapters. It's a good challenge worthy of anyone who loves music enough to study it.