II.

Settings of the Proper

In Gregorian chant, as this collection plus later additions came to be known, the melodies of the Proper are particularly important, especially the Introit (Entrance), Gradual, Alleluia, Tract (Psalm), Offertory, and Communion. Even in the earliest polyphony (multipart music), about 900 to about 1250, settings of the Proper were most common. In these, the chant melody was used as a cantus firmus (fixed melody) to which additional voice parts were added. An important early collection of polyphonic Graduals and Alleluias is the Magnus Liber Organi (1175?), written in Paris by the liturgical composer Leonin (flourished late 12th century) and expanded by his successor Pérotin (flourished 1200). About 1250, polyphonic composition based on chants of the Proper greatly diminished.