ChoralTracks.com is a project of Matthew Curtis and its purpose is to provide tutorials on part singing for music used in liturgy, with a mostly Catholic bent. He has a specialty is producing videos that help singers learn their part, and yet it is clear from the samples that this is not only about singing the right note in the right place. He is offering some beautiful examples of pronunciation and interpretation as well. His list of completed projects for mixed voices is long and so is the list of forthcoming ones. We wish him every success here.
Let me add that Curtis's skill is...beyond belief really. This is one man, one voice. Check it out: