Tetrachords

Part of speech: noun

Definitions

1. A musical structure consisting of four notes typically forming the interval of a perfect fourth
2. A sequence of four pitches arranged in ascending or descending order used in both Western and non-Western music theory
3. A grouping of four tones that serves as a basis for scales, often found in the analysis of melody and harmony in music composition

Etymology: The word is a plural, so its first job is to point to the singular, "tetrachord," a term for a four-note unit. Its core is the Greek "tetra-," meaning "four," which English borrowed as a combining form, and "chord," which in this sense refers to a string, so a tetrachord is literally a four-stringed or four-note span. The concept is old: ancient Greek musicians built their scales from linked groups of four notes spanning a perfect fourth, and the term describes that structure directly. The "tetra-" element is what links it to a whole family of English words. Tetrahedron, tetrapod and tetrarch all share the same Greek number-prefix, which is why the word reads as a piece of a larger scientific-sounding vocabulary rather than a single everyday musical term. Its ancient Greek ancestor, "tetrachordon," was used in the same musical sense, so English is reviving a classical technical term rather than inventing one.