Music theory is the language of music and the study of how music is put together. Having an understanding of music theory is helpful in many ways. For example, when teaching it is much easier & quicker to communicate ideas to a student if the student has a good knowledge of theory. If you play in a band ideas can be passed around and expressed clearly and concisely if the members have good theory knowledge. For lead guitarists theory helps you put the right scale with the right chords. For writers and composers it provides clear direction on chord progressions and melody.
Almost all of the top guitarists today have a good knowledge of theory as well as strong technique. If you want to join them you will need the same.
Music was around a long time before theory came along so it could be said that theory is just a way of writing down and remembering things that sound good. I have come across students who have no musical knowledge what so ever but have written some great music. When we have sat down and analysed what they have written we have found that their music conforms with accepted music theory. The reason for this, I believe, is that we grow up listening to music and are conditioned to hear music in a certain way. Therefore when we write music it conforms to the musical patterns we have grown up listening to. If somebody can write music with no theory knowledge what is the point of learning theory? By learning why your music sounds a certain way theory can help you recreate that sound or avoid it. It should also open up new musical avenues for you to explore.
Finally, music theory will help you gain an insight into how your guitar works. Attempting to jam with other musicians without theory is guesswork usually. Theory gets you straight in and playing something cool which surely is what playing an instrument is about.
Next up: Lesson 2 – Naming the notes