The Rhythmic Modes and Sederunt Principes

Album: Leonin & Perotin: Sacred Music from the Notre Dame Cathedral
Track: "Sederunt Principes" (Track #31)
Composer: Pérotin
Instruments: 4 voices
Musical Form: Conductus
Year: ~1200

The Notre Dame School was renowned not just for polyphony, but also for its use of rhythm, which came in the form of one of six rhythmic modes. These modes can be thought of as groupings of notes with the same relative durations. For example, the first mode is simply a long note followed by a short note. If you skip to 1:45 in "Sederunt Principes", the second-to-last piece on L&P, you can hear the first rhythmic mode clearly in multiple voices, being repeated over the steady drone of the lowest voice. The full set of modes are as follows:

1) long - short
2) short - long
3) long - short - medium
4) short - medium - long
5) long - long
6) short - short - short

Pérotin utilizes a variety of modes in Sederunt Principes, most frequently the first, third, and fifth modes. Listen to the whole piece and see if you can identify modes as they pop up in the different voices, keeping in mind that voices aren't always in the same mode at the same time.

The piece is also worth a listen in its own right. The way it slowly shifts in rhythm and pitch structure, I am reminded of modern minimalist composers such as Philip Glass and Steve Reich; in fact, the latter acknowledges drawing inspiration from Pérotin. This fact alone reassures me that I haven't wasted my time revisiting the music of the ancient world.

External Links: YouTube