On the intonalist blog, a harmonization of the Mass XVII Agnus Dei, intended to be sung a cappella (SAB) and tuned perfectly. I intend to provide this, and others as they come along, for free but with a required PDF license stamp. A recoding linked at the blog post, and a pdf attached to this post.

http://intonalist.wordpress.com/2014/02/20/sight-tuning-exercise/

I'd echo many, though not all, of the sentiments in the lovely preface to the 1929 Kyriale Organ Accompaniment.
http://www.ccwatershed.org/media/pdfs/13/07/11/20-08-42_0.pdf

William Copper