melodic recitation formula used in the singing of the psalms and canticles of the Bible, followed by the "Gloria Patri" ("Glory Be to the Father") during the chanting of the liturgical hours, or divine office. In the Gregorian chant repertory there are eight psalm tones. Because each psalm verse is divided into two halves, the psalm tones have a binary, or two-part, form. The first part consists of the initium, or intonation, of a melodic fragment; tenor, or recitation note; flexa, or downward inflection, used only if the first half of the verse is long; and mediatio, or middle cadence (resting point). The second part comprises the tenor, sung until the terminatio, or final cadence
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