What Is Music Theory?
Understanding music theory means knowing the language of music. The main thing to know about music theory is that it is simply a way to explain the music we hear. Music had existed for thousands of years before theory came along to explain what people were trying to accomplish innately by pounding on their drums. Don’t ever think that you can’t be a good musician just because you’ve never taken a theory class. In fact, if you are a good musician, you already know a lot of theory. You just may not know the words or scientific formulas for what you’re doing.
The concepts and rules that make up music theory are very much like the grammatical rules that govern written language. Being able to transcribe music makes it possible for other musicians to read and play compositions exactly as the composer intended. Learning to read music is almost exactly like learning a new language, to the point where a fluent person can hear a musical conversation when reading a piece of sheet music.
There are plenty of intuitive, self-taught musicians out there who have never learned to read or write music and find the whole idea of learning music theory tedious and unnecessary. However, just like the educational leaps that can come with learning to read and write, music theory can help musicians learn new techniques, perform unfamiliar styles of music, and develop the confidence to try new things.
What is important to remember, though, is that music theory is to composers what grammar is to poets. Music theory can tell you what musicians and composers have done in the past and why it works, but it doesn't dictate what you have to do. Just as poets aren't limited to the strict rules of grammar, musicians, too, have the poetic license to ignore certain "rules" of music theory in order to create the piece they want to create.
However, the inescapable fact is this: you get out of music what you put into it. If you want to be able to play classical music, you must be able to keep a steady beat, and understanding how the harmonies fit together can make it much easier to play because you can see what's coming before you even get there. If you want to be a rock musician, then knowing the notes you need to play in a given key is especially important. Learning to play and understand music takes a lot of personal discipline, but in the end, it's worth all the hard work.