What is the harmonic system based on the third called?

The harmonic system based on the third is known as Tertian Harmony. This term refers to a method of building chords and harmonies that are constructed primarily using intervals of the third. In this system, triads, which are the building blocks of harmony, are formed by stacking thirds on top of one another. For instance, in a major triad, the notes are separated by major thirds, while in a minor triad, the notes are separated by minor thirds.

Tertian Harmony forms the basis of much of Western music from the Common Practice Period (approximately 1600 to 1900) and plays a crucial role in the development of functional harmony, where chords have specific roles within a key. The use of thirds creates a framework for both major and minor tonalities, allowing for the rich harmonic language found in classical music, jazz, and much modern music today. Tertian harmony provides a structured approach to creating progressions that have a sense of resolution and direction.

While other harmonic systems like Linear Harmony may emphasize melodic lines or progressions based on consecutive steps without the same focus on chordal structures, and Modal Harmony may work within the confines of specific modes rather than tonal centers, the distinctive feature of Tertian Harmony is