Gradual

The Gradual, introduced in the 4th century, also developed from a refrain between psalm verses. Later it became: opening melody (chorus)—psalm verse or verses in a virtuosically embellished psalmodic structure (soloist)—opening melody (chorus), repeated in whole or in part. The Alleluia is of 4th-century Eastern origin.…

…office, and the Alleluia and Gradual of the mass. In most cases the basic pattern is R V R, with the V section being one or a few psalm verses. In the Gradual, the final refrain, or responsory, is usually omitted, making the form R V. Within the divine office,…