Medieval France. An Encyclopedia

the first six lines of the hymn Ut queant laxis/Resonare fibris (Ut, Re, Mi, Fa, Sol, La),
helped beginners learn to sing. The note names of this system were used in the West
throughout the Middle Ages and beyond.
TETRACHORD. In medieval music theory, a scale segment of four notes. The three
possible patterns of tones and semitones within a tetrachord (T-S-T; S-T-T; T-T-S) were
significant in some descriptions of the church modes.