      This selection is based on a Gregorian chant which has been altered rhythmically to help blend it with the other three voices.  The cantus firmus is found in a lower part called the tenor.  The overall musical structure of this movement is 
A  (Agnus Dei I), B  (Agnus Dei II), A  (Agnus Dei III.)  
	The text is the same for each of the larger sections except for the final phrase and the texture is similar in each part.  Notice the fullness established through the melodic equality of all parts.  Notice the sonority of the cadences which end on consonant hollow intervals of unisons and fifths.  The phrasing is long and irragular to our ears and seems to nearly come to rest but moves on as the voices independently overlap.