I went to a concert of Advent, Marian, and Christmas Music by the Prolatio Singers & Players, this afternoon. It was really different. Prolation is a subdivision of the rhythmic system which in Medieval Music governed the proportionate duration of the semibreve and the minim. And Medieval it sounded, especially Dennis Ferguson's Mi Atyank Ata Isten. Mi Atyank is a 16th century Hungarian carol. Ferguson arranged it such that tenors and altos augment each other. The first stanza was the original. But after that several composition devices are used. Tenors sing the melody as basses mirror the tune. Altos sing it a fifth higher in augmentation. Sopranos also sing in augmentation, but at pitch and in retrograde. Lastly, the Sopranos sing the original melody in duple time as the other three voices sing in three different pentatonic modes simultaneously. Hence they are called the Prolatio Singers. Very nice.
The other works use three voice for antiphons and two solo voices for verses--typical of Medieval times. There were also recorders and a cello.
It was such a nice afternoon with a nice way to spend Advent.