noun
definition
Any set of four different pitch classes.
definition
A series of four sounds, forming a scale of two-and-a-half tones.
Examples of tetrachord in a Sentence
So persistently does the human ear rebel against the division of the tetrachord into two greater tones and a leimma or hemitone, as represented by the fractions 9, 9, 26, that, centuries before the possibility of reconciling the demands of the ear with those of exact science was satisfactorily demonstrated, the Aristoxenian school advocated the use of an empirical scale, sounding pleasant to the sense, in preference to an unpleasing tonality founded upon immutable proportions.
Claudius Ptolemy (130) rectified this error, and in the so-called syntonous or intense diatonic scale reduced the proportions of his tetrachord to s, iii, f, -i.
As this note is in the upper tetrachord of the scale, the raga is then classified as a morning raga.