Great piece. Years past I searched for a usable edition and failed to find one, but maybe it has been put together recently. I used to own a record (LP) with a recording, so the singers must have had something to use ...
I know; so annoying! I've seached high and low, and only found a partial copy in Google-books. I've found many editions of Perotin, on CPDL & IMSLP, but not the Leonin. I've heard many recordings, so there must be a score somewhere. Maybe.
The staff at a university music library could probably answer this. Some works are published in academic journals or music book series, if not in conventional performing editions.
The Norton Anthology of western music, ancient to baroque, has it on one of the six CDs in the set. Lots of other good chant and polyphony too. I thought it was very well done.
I can't search here at home to find the book today, due to a temporary back outage. However, I can state that the scores in the Anthology are rather small and they are reproductions; so if you can find where the editors reproduced it from, that might be a better-sized version. Failing that, the Anthology's version may suffice. Note: the contents of this textbook change from one edition to another, so buying an old edition may need some care to make sure it has the work you want.
Just found (and ordered) a book put out by the ensemble TONUS PEREGRINUS with the performing editions that they used on their CD of Sacred Music from Notre-Dame Cathedral (NAXOS 8.557340) on LULU! It arrived today and I couldn't be happier, it's a wonderful edition. If you have been looking for these pieces in a usable edition get it!
I have recently purchased a copy of a book entitled "The Rhythm of Twelfth-Century Polyphony." It has a huge section of transcriptions from the Magnus Liber Organi. If you can get your hands on a copy, it will have additional material in it. I found mine for around $30.
Thank you for posting that resource; I will definitely be getting it.
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