Of the portions of the Mass that may be sung, some are chanted solo at the altar with choral response; there are also nine hymns for the choir. Four of these are proper and related in theme, with texts usually from the Psalms: introit, anthem after the epistle (alleluia, gradual, tract, or sequence), offertory, and communion. The five ordinary choral pieces are Kyrie eleison, Gloria in excelsis, Credo (see creed), Sanctus, and Agnus Dei. Plainsong is prescribed for all texts, but latitude is permitted the choir. A musical setting for the five ordinary hymns, called a Mass, has been a major musical form. The principal period of Mass composition lasted from 1400 to 1700. It came to an end with shift of interest to instrumental music, although later composers did use the form. Among the many composers who produced Masses are Josquin des Prés, Palestrina, Monteverdi, Bach, Haydn, Mozart, Beethoven, Verdi, and Stravinsky.