In the shadow of a rising Gothic cathedral, two composers — Léonin and Pérotin — stacked voices upon the ancient chant and, for the first time in history, wrote down rhythm. Western music learned to move in parts.
History of Early Music · No. 02 — The First Polyphony
The Notre-Dame School was a loose circle of composers and singers active at the cathedral of Paris from roughly 1160 to 1250. Building on plainchant, they created the first great repertory of measured polyphony — music in several independent voices, with rhythm precisely notated. It is the true beginning of the Western art of composition.
Two, three, even four independent voices sounding at once — not one line, but many woven together.
Rhythm is written down for the first time, through the six rhythmic modes of long and short.
Organum adorned the solo portions of the chants of the Mass and Office on the greatest feast days.
Collected in the Magnus liber organi — the "great book of organum" — the era's central source.
"Ars antiqua" ("the old art") is the later name for this 13th-century Parisian style — old, that is, only by contrast with the Ars Nova that followed it a century on.
The music grew hand in hand with the building. As the stone rose over the Île de la Cité, the sound rising within it grew ever more elaborate.
The new Notre-Dame de Paris, begun in 1163, was a marvel of the emerging Gothic style: soaring vaults, pointed arches, and vast stone spaces that rang with a long, luminous echo.
Such acoustics invited sustained sound. Hold one low note beneath a moving melody, and the cathedral itself seems to harmonise. Paris was also home to a great cathedral school — the seed of the University of Paris — an intellectual centre where the idea of measuring and notating rhythm could take root.
Acoustics: stone vaults sustain a low tenor into a shimmering drone.
Learning: the cathedral school bred theorists able to codify rhythm.
Wealth & prestige: a great church demanded music grand enough to match its stone.
Liturgy: the most solemn feasts called for the most elaborate adornment of the chant.
Organum was reserved for the soloists' portions of the most important chants — a jewelled setting around the plainchant that the full choir still sang.
Léonin (Leoninus, active c. 1150s–c. 1201) is the first composer of polyphony whose name we know. The theorist known as Anonymous IV calls him optimus organista — "the finest composer of organum" — and credits him with compiling the Magnus liber organi, the "great book of organum".
A cycle of two-voice settings covering the soloists' chants for the Mass and Office across the whole church year.
Two voices: a slow chant tenor below, a single florid upper voice (duplum) spinning above it.
For the first time we can attach a person to a body of polyphony — the beginning of composers as we know them.
Léonin's book survives only in later copies revised by his successors, so his exact hand is hard to isolate — but the tradition names him as its founder.
Pérotin (Perotinus, active c. 1200), called optimus discantor — "the finest composer of discant" — took Léonin's book and made it grander still. He tightened its rhythms, rewrote many sections, and above all multiplied the voices.
Three voices — a tenor beneath two upper voices interlocking in measured rhythm above the held chant.
Four voices — the astonishing Viderunt omnes and Sederunt principes, colossal towers of sound.
Where Léonin flows freely, Pérotin pulses — crisp, dance-like modal rhythm binds all the voices together.
Over a single held tenor syllable, Pérotin's upper voices can spin for minutes — sound piled on sound until the whole cathedral rings like a great chord held in the air.
Take a phrase of plainchant. Stretch its notes into immensely long, sustained tones in the lowest voice — the tenor (from Latin tenere, "to hold"). Above that slow foundation, let one or more voices sing florid, quick, measured melodies. That is organum.
The chant is still present — but so slowed that a single syllable may last half a minute, while the voice above dances through dozens of notes over it.
Within a single piece the music breathes between two contrasting textures, following the pace of the chant's original notes.
Used where the chant moves in long notes. The tenor holds each pitch almost motionless while the upper voice floats freely above in unmeasured, florid melody. Spacious, timeless, cathedral-like.
Used where the chant moves quickly. All voices move together in strict measured rhythm, note against note. These self-contained rhythmic sections are called clausulae — and would give birth to the motet.
The change of texture is dramatic to hear: floating, weightless organum purum suddenly locking into the crisp, pulsing tread of discant, then dissolving again.
Here is the essence of Léonin's art in miniature: a single tenor note, held for the whole passage, while the duplum above spins a florid, measured melody with the long–short lilt of the first rhythmic mode. Pure Pythagorean tuning makes the framing fifths and octaves ring.
Synthesised organ · one sustained tenor (F) beneath a florid, measured duplum · pure Pythagorean fifths
The lowest voice sits on a single pitch for the whole phrase — the chant, hugely slowed.
Above it, the upper voice moves in quick, decorated figures — the melody your ear follows.
Listen for the voices meeting on open fifths and octaves — the "perfect" concords of the age.
Notre-Dame's supreme contribution: for the first time, rhythm was notated. Six fixed patterns of longa (long, ▯) and brevis (short, ▪) — the rhythmic modes — were signalled not by the note-shapes themselves but by how notes were bundled into ligatures. This is the birth of Western rhythmic notation.
The trick: the mode is not shown by each note's shape but by recurring patterns of ligatures (joined note-groups). Once a singer recognised the pattern, the whole passage's rhythm fell into place.
A page of Notre-Dame organum stacks the voices in score, aligned so you can see them sound together. Here is how to decode a short passage of two-voice organum.
Voices are aligned vertically. Read down the page to see which notes sound together.
In the upper voice, the pattern of joined note-groups tells you the rhythmic mode — here, long–short.
The long bars are single chant notes, sustained. One syllable of the word spans the whole passage.
A C-clef or F-clef names one line, as in chant; every pitch is read relative to it.
Pérotin's boldest step was to add more voices. In a discant clausula, all the parts move together in measured rhythm. Here three voices tread the long–short modal pattern in step, opening and closing on the open, ringing sonorities the age prized — a perfect octave and fifth.
Synthesised organ · three voices moving together in modal rhythm · closing on an open octave-and-fifth
The chant foundation — here it moves too, but slowly, anchoring the harmony.
Two upper voices interlock above, each in the same crisp modal rhythm.
The phrase settles onto a hollow, radiant octave-and-fifth — no sweet third yet.
The rhythmic discant sections — the clausulae — proved so appealing that composers began to lift them out as free-standing pieces. Then someone added new words (French: mot) to the upper voice — and the motet, the central form of the next two centuries, was born from the body of Notre-Dame organum.
A self-contained discant section over a fragment of chant tenor, all voices in measured rhythm.
New words set to the upper voice turn the wordless clausula into a texted piece — a motetus.
Voices gain different texts (even different languages), and the motet grows into an art of its own.
So the two great inventions of Notre-Dame — measured rhythm and layered voices — flow directly into the Ars Nova of Machaut and, ultimately, into the whole later history of counterpoint.
Almost everything we know about Léonin and Pérotin comes from one source: a treatise by an unnamed English student in Paris around 1275, catalogued by modern scholars as Anonymous IV. Writing generations later, he preserved the two names that would otherwise have vanished entirely.
"Magister Leoninus was the finest composer of organum, who made the great book of organum for the Mass and the Office to enlarge the divine service. And it was in use until the time of the great Pérotin, who shortened it and made many better clausulae, being the finest composer of discant."
— Anonymous IV, English music theorist writing in Paris, c. 1275 (paraphrased translation)The music itself survives chiefly in three great manuscripts (known as W1, F and W2), copied elsewhere in the 13th century — the Parisian originals are lost.
Pérotin's Viderunt omnes is the classic starting point — four voices piling ecstatically over a single held chant note.
The Notre-Dame School stands at a hinge of Western music. Before it, one line of chant; after it, the endless possibility of many voices in measured motion. Its two inventions — notated rhythm and layered polyphony — are the DNA of everything from the medieval motet to the symphony. To hear Pérotin is to stand at the source of counterpoint itself.
The rhythmic modes are the first system for writing down duration — the ancestor of every time signature.
Léonin and Pérotin are the first named authors of polyphony — the beginning of the composer as an individual.
The clausula grew into the motet, the great form that carried polyphony into the Ars Nova and beyond.
"...being the finest composer of discant, better than Léonin."
— Anonymous IV on Pérotin, c. 1275 — the earliest surviving verdict on a Western composerc. 1160 – 1250 · Paris · where music first learned to move in parts.