"The Oxford Companion to Music describes three interrelated uses of the term 'music theory.'"
The foundations of music, including rhythm, melody, harmony, and notation.
Pitch and Frequency: Understanding the concepts of pitch and frequency, and how they are related to one another.
Scales and Modes: Understanding what scales and modes are, how they can be divided into diatonic and chromatic scales, and their various intervals.
Chords: Understanding different types of chords and how they can be constructed. This includes triads, seventh chords, and extended chords.
Key Signatures: Understanding how key signatures work and how they are represented in sheet music.
Time Signatures: Understanding the different types of time signatures, how they are notated, and how they affect rhythm.
Rhythm: Understanding note values, rests, and how to read rhythmic notation in sheet music.
Intervals: Understanding what intervals are, how to measure them, and how to identify them by ear.
Melody: Understanding how melody is structured, how it relates to chord progressions, and how to create compelling melodies.
Harmony: Understanding different types of harmonic progressions and chord substitutions, and how they can be used to create interesting chord changes.
Instrumentation and Arrangement: Understanding how different instruments work together in an arrangement, and how to write for specific instruments.
Counterpoint: Understanding how to write counterpoint, both in strict rules and in a more free-form style, and how it can be used to create complex harmonies.
Music Analysis: Understanding how to analyze a piece of music in terms of form, harmony, melody, and rhythm.
Ornamentation: Understanding how to add ornamentation, such as trills and grace notes, to a melody.
Dynamics and Articulation: Understanding how to use dynamics and articulation to convey musical expression and emotion.
Musical Terminology: Understanding common musical terminology, such as forte, piano, legato, and staccato, and how they relate to musical expression.
Harmony: Is the study of how chords are constructed and how they work together to create melody and harmony.
Counterpoint: Is the study of how multiple melodies interact with each other to create a unified piece of music.
Analysis: Is the process of breaking down a piece of music into its individual elements and understanding how they work together.
Music history: Is the study of how music has developed over time, including the styles and techniques used in different periods.
Musical form: Is the study of how musical pieces are structured, including the different types of musical forms.
Tuning and temperament: Is the study of different systems of tuning and how they affect the sound of music.
Perception and cognition: Is the study of how the human brain perceives and understands music.
Aesthetics: Is the study of the nature of beauty and its role in creating and appreciating music.
Pedagogy: Is the study of how to teach music theory and other aspects of music to students.
Performance practice: Is the study of how music was performed in different periods and how to best interpret and perform music today.
"The first is the 'rudiments', that are needed to understand music notation; the second is learning scholars' views on music from antiquity to the present; the third is a sub-topic of musicology that 'seeks to define processes and general principles in music'."
"The musicological approach to theory differs from music analysis 'in that it takes as its starting-point not the individual work or performance but the fundamental materials from which it is built.'"
"Music theory is frequently concerned with describing how musicians and composers make music, including tuning systems and composition methods among other topics."
"A more inclusive definition could be the consideration of any sonic phenomena, including silence."
"The study of 'music' in the Quadrivium liberal arts university curriculum... was an abstract system of proportions."
"Music theory as a practical discipline encompasses the methods and concepts that composers and other musicians use in creating and performing music."
"The development, preservation, and transmission of music theory in this sense may be found in oral and written music-making traditions, musical instruments, and other artifacts."
"Ancient instruments from prehistoric sites around the world reveal details about the music they produced and potentially something of the musical theory that might have been used by their makers."
"Practical and scholarly traditions overlap, as many practical treatises about music place themselves within a tradition of other treatises, which are cited regularly just as scholarly writing cites earlier research."
"Etymologically, music theory is an act of contemplation of music, from the Greek word θεωρία, meaning a looking at, a viewing; a contemplation, speculation, theory; a sight, a spectacle."
"Music theory, as such, is often concerned with abstract musical aspects such as tuning and tonal systems, scales, consonance and dissonance, and rhythmic relationships."
"There is also a body of theory concerning practical aspects, such as the creation or the performance of music, orchestration, ornamentation, improvisation, and electronic sound production."
"University study, typically to the MA or PhD level, is required to teach as a tenure-track music theorist in a US or Canadian university."
"Methods of analysis include mathematics, graphic analysis, and especially analysis enabled by western music notation."
"Comparative, descriptive, statistical, and other methods are also used."
"Music theory textbooks... often include elements of musical acoustics, considerations of musical notation, and techniques of tonal composition (harmony and counterpoint), among other topics."