Not much to add to Wisty's review really, but this was so unexpected a delight I had to write something. Unexpected, because this early English stuff can seem rather dull - but there is huge variety within the framework the group set for themselves here. Some of the word-setting is so rapid that the singers are almost falling over themselves, at other times it's so melismatic the words hardly seem to change. Ad the variety between the number of vioces, and the pieces which (conductus-like) move in 'vertical' (homophonic) style versus the (motet-like) 'horizontal' polyphony of melodies moving against each other, and you have a truly delightful collection of anonymous - and therefore underrated - pieces. A reminder that anonymous does not mean inferior, it simply means we don't know the name(s) of the skilled composer(s) who wrote these pieces.
I first encountered French ensemble Diabolus in Musica with their outstanding disc of Notre Dame compositions (Paris expers Paris), which contained many items I had not heard before. It looks like DiM perhaps go out of their way to record less familiar material, such as that here from English Royal chapels around the period of the Hundred Years war.
There is a mixture of conduit and older motet forms (that is to say with two, three or even four different texts sung simultaneously, whereas on the continent at this time the newer 'isorhythmic motet' form had already taken over, which led to the motet form more familiar to most from Renaissance polyphony), for between 2 and 5 voices, but mostly 3 or 4; some are quite unusual in their structure.
The accompanying booklet contains decent historical notes in French and English, along with the texts of the pieces themselves plus English & French translations.
Beautifully performed pieces, and hats off to DiM for trying something a little different by selecting this material.