____13. It is a single line of text and melody sung either by the priest or by several voices of the choir in unison. ____14.It conveys calm and represents the voice of the church. _____15. Its rhythm is flexible without meter and has a little sense of beat. _____16. It is the long tenor notes of the chant, though usually too drawn out to be easily heard as melody. ______17. It became a truly polyphonic and the melody added to the chant. . _____18. It is a plainsong served as a symbolic reminder of the music's liturgical meaning. . _____19. The motet derives from the French mot which may refer to the added texts in the upper parts. _____20. The cantus firmus motet had become a sophisticated and complex from testing the skills and inventiveness of composers of the full. _____21. It is a melodies where used in medieval churches and monasteries.