In the scope of harmony, there are many types such as functional harmony, ethnic harmony, counterpoint harmony, and modern harmony. Functional harmony (also known as traditional harmony) was created by the European classical music school and romantic music school.

Harmony is the pitch organization form of multi-part music and one of the basic means of expression of music. As far as the general concept of composition theory is concerned, harmony is the technical category corresponding to counterpoint (that is, commonly known as "polyphony"). In music practice for more than a hundred years before the 19th century, harmony has always been regarded as the basis of counterpoint.

Since the 17th century, due to the gradual development of main-key music, the role of harmony has become increasingly important. Its role in music generally has three aspects:

①The combination of voices. On the basis of unified harmony, the various parts combine with each other to form a coordinated whole.

②The structural role of music. Harmonic progression, closing patterns, tonal layout, etc. play an important role in composing the musical form.

③The performance role of content. Shape the music image and express the music content through the color and texture of the harmony and other factors. The processing of harmony is an important writing skill in music creation, and it is also the basis for other composition techniques such as counterpoint, orchestration, and musical form. Sometimes tunes are also derived from harmonies.