I've been talking to a friend of mine about all things chant, from the propers, to the reforms in Tra Le, the difference between the GR and GS, the original lineless notation that was learned by rote, and everything else, and he's wondering if there is a website where you could find a good history of gregorian chant.
The Wikipedia page is a decent start. But best is just to buy second hand Willi Apel's book (Gregorian Chant - published 1958). Or David Hiley's acclaimed Western Plainchant - a Handbook (1993) or his more recent Gregorian Chant (2009). Attached, but without illustrations, is an edited version of a reading given by John Caldwell on the history of plainsong. Or look on the Musica Sacra site (Literature) for downloads on the history of chant (e.g. Saulnier's: Gregorian Chant, a guide).
The new edition of the Catholic Encyclopedia has an article on the topic which is also very good. IIRC, it was written by Fr. R. Skeris, Ph.D., a most legitimate liturgist.
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