I am unqualified to give a technical review, but I know it sounds beautiful. This CD was highly recommended upon release, so I gave it a go, having a large classical collection but not particularly enjoying most choral music.
The first piece by the later monk-composer Perotin, Beata Viscera, is a piece for one voice, here sung by Rebecca Hickey, whose voice rises and falls in the spaces of the Abbey of Chancelade in France with beguiling beauty. Let this be a good guide to the enjoyment of the rest of the CD, which explores a key period in the development of religious music, when the Plain (Gregorian) chant was being added to and superceded by the multi-voiced (two, then four, etc) pieces that Leonin and Perotin composed for the Abbey of Notre Dame in Paris, whose soaring Gothic arches were newly built and creating new spaces for worship, sound and thought.
Tonus Peregrinus, the eight-part group of singers, do not just give us a medley of these pieces, but show how they developed both in technical demands, in compositional detail and in how the pieces could sound in these new light-filled temples of the twelfth century.
At times we hear male voices chanting over a drone, then joined by more voices singing different lines, at times the whole group come in to add their glory to the text. After track 30 we hear a peaceful moment with the abbey bell chiming, and as it falters away so begins thirteen minutes of Perotin's 'Sederant principe,' a piece here sung by the ladies instead of the usual boys. This is glorious multi-voiced music, constantly moving and rising and interchanging with angelic sounds all through. The power of the female voices, I think, gives it more feeling than boy voices probably could. It never fails to make me shiver, most beautiful.
I recommend this CD for the beauty and thoughtfulness of the entire project, the result is well worth it!