Music theory is the study of how music works, the building blocks of music, and what is needed to understand music notation. For the beginner, music theory is the study and descriptions of music rudiments required to notate and read music, such as key signatures, time signatures, rhythmic notation, pitches (notes), scales, modes, chords, tensions, and elements of composition such as rhythm, harmony, melody, and counterpoint.
There is no single definition that describes all the parts of music theory. As a practical discipline, music theory is concerned with the fundamentals of how music is made, and also with analysis of sounds, including silence, and how they relate to music.
Modern music theory textbooks often include descriptions and analysis of practical applications of the harmonic series, musical acoustics, orchestration, improvisation, scales, tonal and rhythmic relationships, instrumental performance, and electronic production. While this might seem like a lot of information, beginners should focus on just the basics, which limits the scope and makes it easier to make good progress quickly.
What is taught in music theory?
The basic elements of Music Theory include melody, rhythm, harmony, form, pitch, and scales. More advanced topics include modes, composition, counterpoint, orchestration, performance, improvisation, tuning systems, consonance, dissonance, and electronic sound production. Anyone can learn the basics of Music Theory, with or without a teacher, but for learning advanced topics, formal study is usually required.