Music has rules for composition and performance. Theory is the study of how all these rules work and come together to produce a great piece of music. It is important to understand the principles of theory in order to compose, understand and play the music. Students who study theory learn the basic of harmony, how scale work, how to rewrite music in another key, tempo, dynamics and a whole lot of Italian words for these things. Theory can be taught privately and in the group setting as well. Students who are taking RCM exams should take theory classes because that is the part of the program.