The last four melodies in Rutter's Eleven Gregorian Chants are Four Antiphons of the Virgin Mary, compositions from between the eleventh and thirteenth centuries which closed the office of Compline (the last Office of the day). An Antiphon is the root of 'Anthem' (Old English antefne), meaning a song of praise or devotion. The Marian antiphons are anthems sung to the Virgin Mary, using independent texts without psalms. Here are some links to Gregorian notation and performances. These Marian hymns can also be found gathered here.
Alma Redemptoris Mater
Written by Hermannus Contractus (Herman the Cripple, 1013-54). Like the others below, this is given int he longer version known as 'Solemn Tone'. Opening with a long melisma, this is sung at the Advent to Candlemas. There are some comments by musicologists and other information here.
Ave Regina caelorum (Candlemas to Holy Week). The Marian hymns were used as the basis for many arrangements in the Renaissance and later. There is a useful gathering here of some of these polyphonic versions.
Regina caeli laetare (Easter Even to Pentecost). See this site for different versions and performances.
Salve Regina
Sources and Further Reading
History and background to Marian Antiphons
Entry by Richard Taruskin from Oxford History of Western Music
