What is mensural notation and why does Measuring Polyphony use it?

Mensural notation is the system of rhythmic notation that emerged in the thirteenth and fourteenth centuries to specify the duration of notes, and it is the notation in which almost all polyphonic music from 1300–1600 was written. Measuring Polyphony uses it because the project's goal is to present late medieval polyphony in its original notational form—encoded in a machine-readable format and linked to manuscript images and audio—rather than translating it into modern notation.

What "mensural" means

The term comes from the Latin for "measurable." Before this system, pitch could be notated with reasonable precision, but rhythm could not be measured in fixed durational values. From the thirteenth century onward, techniques for specifically notating rhythmic duration emerged, and this notation is what scholars call "mensural" or "measurable." Its rules changed little after about 1350, which is why a single notational framework can cover roughly three centuries of repertoire.

Two features define the repertoire Measuring Polyphony works with:

• Polyphony — music composed for two or more parts.
• Mensural notation — the rhythmic system those parts were written in.

Why the project encodes the original notation

Modern print editions stand between today's readers and the original experience of this music in two distinct ways:

1. Notational translation. Editors convert mensural notation into modern notation, so the reader never sees the rhythmic system the composer actually used.
2. Book-shaped sorting. Editions arrange the repertoire according to conventions of the printed book—volumes or series ordered by composer, genre, or country—rather than by how the music survives in its manuscripts.

Measuring Polyphony takes the opposite approach. It presents digitisations of polyphonic compositions copied in thirteenth- and fourteenth-century manuscripts in mensural notation, linked where possible to high-resolution images of the original manuscript sources and to MIDI audio files. The point is to keep the music inside its original context rather than replacing that context with a modern editorial frame.

How the encoding works

The project relies on two things:

• Digital image repositories of music manuscripts, which supply the manuscript images.
• The Music Encoding Initiative (MEI), a community-based standard for encoding music notation, which supplies the machine-readable format.

Encoding the medieval notation in a standardised format means the music data can potentially be searched or analysed—something a scanned page or a printed edition cannot offer on its own.

What the project is trying to achieve

Measuring Polyphony states three goals:

• Make transcriptions and audio freely available online to performers, scholars, and the general public, presented alongside images of the original music manuscripts.
• Encode the medieval notation in a standardised machine-readable format so the music data can potentially be searched or analysed.
• Continue developing the project, which began when project director Karen Desmond was at the Schulich School of Music at McGill University and now continues at Brandeis University.

Why this matters for anyone using the site

If you want to study, perform, or teach this repertoire, the choice Measuring Polyphony makes has practical consequences. You get the notational evidence itself—what the scribe wrote—rather than an editor's resolution of it, and you get it next to the manuscript image, so you can check the encoding against the source. That makes the site useful for questions about how a piece was notated, not just how it sounds. If you only need a modern performing score, a conventional edition may still be the faster route; Measuring Polyphony is built for the opposite purpose.