Tetrachord |

Greek tetraxordon, lit. – four-string, from tetra, in compound words – four and xordn – string

A four-step scale in the range of a perfect fourth (eg, g – a – h – c). The special position of T. among monodich. modal structures is determined by the interaction of 2 primary factors of modulation – linear (associated with movement along the tones of the scale from the stand) and harmonic (respectively – with the opposition of consonant and dissonant relations). The role of consonance as a regulator of melodic movement first acquired the narrowest of the consonances – the fourth, the “first” consonance (Gaudentius; see Janus C., “Musici scriptores graeci”, p. 338). Thanks to this, T. (and not the octachord and pentachord) becomes the main one before other scales. cell of the modal system. Such is the role of T. in other Greek. music. The consonant edge tones that form the core of T. (“fixed” – estotes, “gestuts”) are the abutments in it, and the mobile ones (xinoumenoi – “kinemens”) can change, forming within 4 steps decomp. diatonic, chromatic scales and anharmonic. childbirth (see Ancient Greek modes). The combination of rhythms with each other led to the emergence of more complex modal structures (the most important among them are octave modes, the so-called “harmonies”).

Wed-century. modal system, in contrast to the Greek, as the main. models has not T., but more polyphonic structures – the octave mode, guidon hexachord. However, the role of T. remains extremely important in them. So, the totality of the finals of medieval modes forms T. DEFG (= defg in the modern notation system); within the framework of the octave mode, T. remains the main. structural cell.

Guidon’s hexachord is an interlacing of all three dec. according to the diatonic interval. T.

In the structure of the scales characteristic of Russian. nar. melodics, T. of one or another interval composition is one of the most important constituent elements. In some samples of the most ancient melodies, the scale of the song is limited to T. (see Sound system). The structure of the everyday scale, formed by tone-tone trichords with a fourth interval between sounds occupying the same position in adjacent trichords, reflects the non-octave principle and can be represented as a chain of tone-tone-semitone tetrachords (see Perfect system).

References: Janus S., Musici scriptores graeci, Lpz., 1895, reprografischer Nachdruck, Hildesheim, 1962; Musica enchiriadis, v kn.: Gerbert M., Scriptores ecclesiastici de musica sacra especially, t. 1, St. Blasien, 1784, reprogralischer Nachdruck, Hildesheim, 1963.

Yu. N. Kholopov