The same anonymous English student at the Notre Dame school who identified Léonin as the greatest composer of organum, also identifies Perotin as Magister Petronius, or in English, “Pérotin the Master” of organum. He was known for the development of three – part and four – part organa. He was the most famous of all of the composers of the Notre Dame school.
A prominent feature of his compositional style was to take a simple, well-known melody and stretch it out in time, so that each syllable was hundreds of seconds long, and then use each note of the melody (the tenor, Latin for “holder”, or cantus firmus) as the basis for rhythmically complex, interweaving lines above it. The result was that one or more vocal parts sang free, quickly moving lines (“discants“) over the chant below, which was extended to become a slowly shifting drone.
A page from Pérotin’s Alleluia nativitas
In addition to organum, which was liturgical music, Pérotin also wrote conductus, which was sacred but not liturgical, more akin to the modern hymn.
See http://www.youtube.com/watch?v=FvJ6xl3l1ek&feature=related for “ Views of Notre Dame de Paris accompanied by Perotin’s 4-part organum ‘Sederunt principes.’”
See http://www.youtube.com/watch?v=EJxRDhejtwo for Perotin’s 3-part organum Alleluia nativitas.
For a early work for organ in the organum style, Perotin’s “Alleluya. Nativitas” at http://www.youtube.com/watch?v=3QyfuEuxQmo&feature=watch_response.
See http://www.youtube.com/watch?v=Z7OWtlfxAqU for Perotin’s Viderunt omnes in four parts, which I find interesting for several reasons. First, it begins with a forte “Vi-“ which decrescendos dramatically during which the base part drops out. You will also note that he uses a middle voice drone. There is some of the same dissonance which slightly wrenches the listener at significant moments of the music and then resolves, often to close a musical section. Throughout, the video fixes on a portion of an illuminated manuscript, presumably of the music that is sung.
See http://www.classicalarchives.com/composer/7631.html for recordings available for purchase at Classical Archives.
See, also, http://www.classical.net/search/search.pl?Terms=Perotin for other resources regarding Perotin.