The theory of music is the first substantial knowledge one receives from the inexhaustible art of music. It is crucial to create a suitable starting point to provide motivation and inspire young musicians towards the direction of knowledge and creation. For this purpose, after fifteen years of teaching music theory, I feel the responsibility to generously share my knowledge and experience with those who wish to explore the world of music. In this book, the student has the opportunity to both understand the theory and engage in practice through the exercises included at the end of each chapter. In addition to the established material of music theory, this series includes chapters on the presentation of orchestral instruments to provide motivation for the new musician to decide which instrument to pursue in their journey, as well as chapters on proper music spelling, which serve as a launching pad for personal compositional expression.