The Clerks' Group is a supreme group of singers, and these performances of Ockeghem's music are supreme in quality, far outstripping most other groups' recordings by far. It is very hard to find good performances of Ockeghem's music, partly because it is so dense polyphonically. The Clerks' Group has risen to the challenge superbly. I can't rave enough about these recordings.
For some reason, the MP3 downloads on this Amazon site aren't working (not for me anyway), but the recordings can be purchased, @ $.99 per cut, on the iTunes Store.