ritsu scale
An anhemitonic pentatonic scale used primarily in gagaku (Japanese court music), consisting of the notes re, mi, so, la, ti. This is a specialized musicological term.
The ritsu scale is often used in gagaku.
From 律 (ritsu, a term for a mode or scale in traditional Japanese music) + 音階 (onkai, 'musical scale'). The exact historical derivation is uncertain, but the term is firmly established in gagaku theory.