As an example of how one might combine an exercise in sight reading with an exercise in tuning, I made this harmonization of the Agnus Dei from Mass XVIII chant. Needless to say, if you listen, it is a synthesis. But it is tuned correctly.
RECORDING: Mass XVII Agnus Dei (SAB a cappella)
PDF: Mass XVII Agnus Dei
Symbol expanations may be found in an earlier post, but briefly the heavy down triangle is a comma-low modal scale note; the circle+ tonic; the light up and down arrows dominant and sometimes supertonic over dominant, and subdominant; the double heavy down triangle two comma low implied secondary dominant third.
I intend to make this available free, but with each use requiring an explicit license stamp allowing duplication and performance. Contact me directly for such a license. For perusal, naturally, no license at all is needed.