In recent years there has been a renewed interest in Gregorian chant. Most people might think only of the chants of the ordinary of the Mass; the Kyrie, Gloria, Credo, Sanctus and Agnus Dei. People might even think of Gregorian hymns of the past, but there are other prayers during the Mass that people might not be familiar with in their chanted form.
These are the Introit (entrance chant), Gradual, Alleluia, Offertory, and Communion chants. The Gradual in the Graduale Romanum is the same as the Responsorial Psalm in the Lectionary. Few Catholics have heard the option of an Offertory chant from the Graduale Romanum as it is usually supplanted by an Offertory hymn.
Most chant resources for the Propers do not have all the Propers that are available to be sung at Mass. This is particularly true for the Offertory verse. The English Psalm Tone Propers include all five of the Propers and offer the “possibility of immediate implementation with minimum preparation and even the most modest musical resources.”
You can read the full article from The Catholic World Report entitled, “The Renaissance of the Mass Propers” here.