For musical instruments there are a number of hierarchical classification systems in use worldwide, amongst them the well-known but somewhat limited Hornbostel-Sachs system.

I find myself wondering if there are similar systems in existence for music theory, for example by area of application.

To date all I have come up with are (the again rather limited) library (ie media) classification systems such as the Dewey Decimal or American Library of Congress systems.

I'd be grateful if anyone could identify more comprehensive and so to say 'domain-native' classification systems.

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4 Answers 4


Covering the "classical" or "common practice" period are several classification systems. The currently favored one is "functional theory" which describes harmony in term of goals (dominant goes to tonic). To some extent this system stems from Hugo Riemann. More narrowly, Riemann had a "dualistic" theory which treated major and minor chords as being duals of each other and basing more extensive theory on that.

An earlier version is due to Jean-Phillipe Rameau who described chord movements in terms of the "root" of such a chord (thus making chords like CEG and EGC the same in terms of roots.)

Another somewhat different approach is the earlier "thorough bass" approach which describes harmonic movement in terms of the bass (or lowest tone) of the current harmony. Figured bass symbols come from this practice. For the most part, this thorough bass method has some aspects of functional theory and some aspects of a theory based purely on intervals above the bass.

One problem with a taxonomy of music theories is that various authors concentrate on different aspects of music; some concentrate on playing, some on composition, some on analysis. In addition, the time periods covered are different.

A good reference is "The Cambridge History of Western Music Theory" edited by Thomas Christensen.

  • 1
    The Hornbostel-Sachs system provided as an example is an cataloging system with the goal of information recovery. This response is interesting in itself, but does not describe a classification system as implied by the question. Without indexing, no recovery. Jul 23, 2016 at 5:42

According to John Rahn in "Basic Atonal Theory", tonal theory can be considered a special case of atonal theory (p.19) which in turn is a special case of more generalized mappings and operations (p.56). So that is at least one hierarchy that could be constructed.


Wikipedia appear to have developed an own, more or less alphabetic classification structure:

A ► Musical analysis‎
D ► Music diagrams
F ► Musical form‎
H ► Harmony‎
J ► Music theory journals
L ► Music theory lists‎
M ► Mathematics of music
  ► Melody‎‎
  ► Microtonality‎‎
  ► Music theory templates
P ► Philosophy of music‎
  ► Pitch‎
  ► Post-tonal music theory‎
R ► Rhythm and meter‎
S ► Music semiology‎‎
  ► Musical symmetry‎‎
T ► Musical techniques‎‎
  ► Music textbooks‎
  ► Music theorists
  ► Tonality‎‎
Σ ► Music theory stubs

With each division in this list hiding a further subclassification tree, it is appears more immediately comprehensive in scope than the library classification systems mentioned in the original question.

It does, however, go beyond classification of the so-to-say 'technical' or native domain space, straying into areas such as documentation (musical journals, textbooks) and philosophy.

It's real value, I suspect, lies not so much in the structure per se, but it's scope and flexibility.


Here an initial music theory breakdown by time, frequency and dynamics in the form of a Venn Diagram, and which might conceivably form the basis of a music theory classification tree. It is also suggestive of further subdivisions dedicated to (say) orchestration and/or performance.

Though it clearly arose out of practical considerations, for it to be of practical use in future applications, a Dewey-Decimal hierarchy would need to be imposed.

ASIDE: happily, this hierarchy specifically avoids those physical configuration attributes MISSING from the Hornbostel-Sachs instrument classification system, such as number of notes per octave, temperament or intonation, scale length, tuning etc. (With many instruments across multiple cultures sharing similar characteristics, these physical qualities need appended to the HS system to arrive at a comprehensive, if -even then- not quite "name-unique" instrument definition. Here, due to the layering of components from, for example base board through to string / key or other interface element, the order of Dewey-Decimal indexing is critical).

Time-Frequency-Dynamics Breakdown

Source: The Conductor Program

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