I have only recently discovered the liturgical and religious music of Pärt and Penderecki. Pärt hails from Estonia, I believe, and even as I write I am listening to a wonderful, mysterious, and moving Magnificat. I read a short musicological sketch that suggested that Pärt experimented for a time with a twelve-tone system á la Schoenberg, Webern, and Berg. From this he developed a distinctive musical style that some have labelled minimalist and others (perhaps Pärt himself) have called the tintinnabuli style. He seems to limit himself to a very restricted range of notes and frequent repetitions. The end result sounds like something between Gregorian Chant and more elaborate Renaissance Polyphony. It isn't strict Chant because there are definite harmonies in the voices, and yet there is something about it, perhaps all voices together with no additional "background" lines against which lines are sung, that suggests Chant at times.
Anyway, if you have not encountered Pärt, I would heartily recommend him as some of the very finest sacred music of recent times. It is in many cases beautiful and mysterious beyond words. There is a blend of the serene and the exalted that transports the listener into another realm.