Ancient type-melodies for 8 church ('Gregorian') tones. Transcribed from the South-French tonary of the 10th century (Ms.: F-Pn lat. 1121, fol. 201v-205v). Pseudo-liturgical verses with initial numerals (primum..., secundum..., tertia... etc.) helped singers to associate a current model with a 'real' chant (such as antiphon) of the same tone. These type-melodies were probably conceived as didactic, to adjust ear for typical melodic formulae, reciting tones, finals etc. They should not be confused with psalm tones, which represent an exact scheme for modulating psalms and canticles.

Excerpt from Boethius' De musica depicting a scale