pentatonic tetrachord五声调式的四音列
Enharmonic tetrachord四分音四音列
Disjunct tetrachord不连续四阶
Chromatic tetrachord色彩性
Conjunct tetrachord连续四阶
Lower tetrachord下四阶
N（名词） (in musical theory, esp of classical Greece) any of several groups of four notes in descending order, in which the first and last notes form a perfect fourth (尤指古希腊音乐理论中的)四度音阶