So you’re a guitarist. You play by ear, you play what sounds good. You’ve never taken any theory lessons, and that hasn’t stopped you from writing kick-ass songs. Why should you care whether you’re playing in a minor key or a major key? Why should you care about intervals and note names and chord alterations and chord substitutions? Well, I’ll tell you why.
First of all, I’ll admit you obviously don’t have to. Some of the best all-time musicians couldn’t read English, let alone read music. I can’t imagine Robert Johnson and Mississippi John Hurt sitting around discussing augmented fifth intervals. Creating good music is, first and foremost, about what sounds good. What learning theory does is it gives you more tools to work with. Instinct is always going to be an important part of writing, learning, and performing music, but why not add to that? Why not bring another weapon to the battle?
Some are afraid that by studying too much they will lose their natural, childlike instinct for creativity. They’re afraid of becoming automatons, trapped within the rigid shackles of musical ideas that were concocted by long-dead white-haired men. They’re afraid of sounding just like every other music-theory student. They’re afraid the musical process will shift too far to the left side of the brain. These are valid concerns, but with the right approach, the problems can be avoided.
The first thing to remember is that music theory, all of it, is a general guide. There is no hard and fast rule that a song has to use notes that belong to a particular key, or that a song has to maintain a consistent time signature. The better you understand the “rules,” the easier it is to know when to break them, and you can understand why that combination of notes you came up with sounds all cool and sinister.
Theory saves time. Your time. Thousands of years of experimentation and thinking and listening went into the definitions and guidelines we have today. Sometimes that history is a handicap, for example in some of the illogical terminology we’re stuck with. Usually, though, it saves us the trouble of trying the same experiments and learning the same rules of thumb that thousands of others before us already have.
Music is never created in a vacuum. Even if you pick up a guitar and start playing random chords until you find something that sounds good, your definition of what sounds “good” is based on all the melodies, harmonies, speach, or noises you’ve heard in your entire life. Before you were born, you probably heard music. And here’s the best part: so did your audience. Whoever you’re playing for, chances are they have pretty similar ideas of what sounds good, because they were influenced by a similar set of melodies, harmonies, speech, and noises.
Music is all about expectations. The trick is, if you study, you can learn how to manipulate the listener’s expectations. You’ll know how to build tension, you’ll know how to keep them waiting, you’ll know how to bring sweet sweet release. Because that’s what good music does: it sets us up, then knocks us down. It gets us ready, then delivers the goods, building to a glorious climax. Understanding how the different parts of music works together gives you the tools you need to do that like a pro.