Tertia |

from lat. tertia – third

1) An interval in the volume of three diatonic steps. scale; indicated by the number 3. They differ: large T. (b. 3), containing 2 tones; small T. (m. 3), containing 1^1/2 tones; increased T. (sw. 3) – 2^1/2 tones; reduced T. (d. 3) – 1 tone. T. belongs to the number of simple intervals not exceeding an octave. Large and small T. are diatonic. intervals; they turn into minor and major sixths, respectively. Increased and reduced T. – chromatic intervals; they turn into diminished and augmented sixths, respectively.

Large and small T. are part of the natural scale: large T. is formed between the fourth and fifth (4:5) overtones (the so-called pure T.), small T. – between the fifth and sixth (5:6) overtones. The interval coefficient of large and small T. of the Pythagorean system is 64/81 and 27/32, respectively? In a tempered scale, a large tone is equal to 1/3, and a small tone is 1/4 of an octave. T. for a long time were not considered consonances, only in the 13th century. the consonance of thirds (concordantia imperfecta) is recognized in the writings of Johannes de Garlandia and Franco of Cologne.

2) The third degree of the diatonic scale.

3) Tertsovy sound (tone) triad, seventh chord and non-chord.

V. A. Vakhromeev