This movie is part of a series of movies where Psallentes sings Machaut’s Ite missa est and Deo gracias. In an introductory movie the manuscript page as a whole is on show. In related movies, each of the four voices can be followed in detail. The audio is always the same. [Video 1 corresponds to the triplum, 2 to the motetus, 3 to the tenor, and 4 to the contra-tenor].
GB-Cccc stands for Great Britain, Cambridge, Corpus Christi College. This library has this Machaut manuscript on loan, it is actually better known as the Ferrell-Vogüé manuscript, which is in the private collection of James E. and Elizabeth J. Ferrell. A facsimile edition has been planned. It is a beautiful manuscript from the fourteenth century, and it may have been made for (or was at least in the collection of) the Count of Foix. Consulted via http://www.diamm.ac.uk (where you can take a look at the whole manuscript). – Hendrik Vanden Abeele