tetrachord

A tetrachord is a musical term referring to a sequence of four distinct pitches. In ancient Greek music theory, it formed the fundamental building block of scales and modes. The term is derived from the Greek words "tetra" meaning four and "chordē" meaning string or interval.

In Western music, the term often describes a segment of a scale consisting of four notes. For instance, in the C major scale, C-D-E-F is an ascending tetrachord. The specific intervals between the notes within a tetrachord are crucial to its character. Common types include the diatonic tetrachord, which can be further divided into types like the major and minor, and the chromatic tetrachord. The intervals are typically described from bottom to top.

Historically, the concept of the tetrachord was central to the development of musical systems, particularly in ancient Greece where composers and theorists like Aristoxenus explored various arrangements of intervals within these four-note structures. These arrangements influenced the creation of scales and modes that formed the basis of melodic and harmonic practices. The understanding of tetrachords has evolved over time, but they remain a significant concept in music theory for analyzing melodic structure and understanding scalar construction.