Measuring Polyphony

Digital encodings of late medieval music

Project Description

The thirteenth and fourteenth centuries saw an unprecedented increase in the production of manuscripts not focused solely on music written for liturgical services, but which contained a diversity of musical styles, genres, and subject matter. These new repertoires were copied in music-only manuscripts, and in manuscripts that interweave songs, texts, and illustrations. At the same time, techniques for specifically notating individual rhythmic durations were developed, a notation called ‘mensural’ or ‘measurable.’ Almost all polyphonic music (music composed for two or more voice parts) from 1300-1600 is notated in mensural notation, the rules of which changed little from c. 1350. Yet modern editions invariably introduce many layers of translation when they present this music: for example, translating the original notation into modern notation that often obfuscates the original’s intent; or categorizing and collating individual music compositions according to the conventions of modern publications, ignoring the presentation context within the original manuscript sources.

‘Measuring Polyphony’ presents, for the first time, digitised versions of polyphonic compositions written during the thirteenth and fourteenth centuries, offering new possibilities for mediating the scholarly and public experience of this richly evocative music within its original manuscript context. The project began at the Schulich School of Music at McGill University, and now continues at Brandeis University. It leverages the potential of the rich digital image repositories of music manuscripts and the community-based standards for encoding music notation of the Music Encoding Initiative (MEI). ‘Measuring Polyphony’ has three goals:

  1. makes transcriptions and audio freely available online to performers, scholars, and the general public, presented alongside images of the original music manuscripts;
  2. encodes the medieval notation in a standardised machine-readable format so that the music data can potentially be be searched or analysed using current tools, and through this interoperability make the data available to other websites and applications; and
  3. streamlines the processes and tools for digitally encoding mensural polyphony so that other stakeholders can easily and rapidly enlarge the dataset.

Project Team

Project Director
Karen Desmond, Brandeis University

Programming of the mensural notation transformation scripts
Martha Thomae Elias, McGill University

Website design, architecture, and programming
Elizabeth Koshelev, Brandeis University

Verovio customization
Laurent Pugin, co-director, Répertoire International des Sources Musicales, Switzerland

Encoding and proofreading
Emily Hopkins, Sam Howes, Sadie Menincain (McGill University)
Shawn Mikkelson, Daniel Shapiro (Brandeis University)

Web interface prototype design
Arya Boudaie, Brandeis University

Advisory Board

Julie Cumming, Professor, McGill University
Ichiro Fujinaga, Professor, McGill University
Richard Freedman, Professor, Haverford University
Andrew Hankinson, Senior Software Engineer, Bodleian Libraries, University of Oxford
Laurent Pugin, co-director, Répertoire International des Sources Musicales, Switzerland
Craig Sapp, Researcher, CCARH/PHI, Stanford University


The following organizations are acknowledged for their financial support:
Office of the Provost, Brandeis University

Mountain View Mountain View

Mountain View

Thanks are also extended to the following individuals and organizations for their advice and support of this project, and for the provision to the general public of open source standards and tools.

Michael Scott Cuthbert, Massachusetts Institute of Technology
Giuliano di Bacco, Assistant Professor, and Director, CHMTHL, Indiana University Jacobs School of Music
Perry Roland, Music Librarian, University of Virginia
Mountain View Mountain View Mountain View
Mountain View Mountain View
Mountain View

The Repertoire

The first stage of this project focused on a representative sample of 64 three- and four-voice French motet repertory that dates from c.1300 to c.1350 (that is, a repertory that bridges the ars antiqua and ars nova) and offers examples of both those styles of music notation. Presented here are 24 motets from the eighth fascicle of the Montpellier Codex, copied in the 1310s; 18 motets from Roman de Fauvel (copied c. 1317) and the Brussels Rotulus (copied c. 1330); and 22 motets from the Ivrea Codex that are also listed in the Tremoïlle Index (both these sources date from the 1370s or later).

Working from the lessons learned during the process of encoding this repertoire, future plans include encoding a larger repertoire of medieval polyphony, most likely another self-contained ars antiqua repertoire, such as the remaining motets from the the eighth-fascicle Montpellier motets and/or the Roman de Fauvel, or from another fascicle of the Montpellier Codex, or perhaps the 100 motets transmitted in the Bamberg Codex. If you have a repertoire of compositions that you would like to encode, and have the time and/or resources to transcribe and proofread your transcriptions according to the process outlined below, please be in touch and we can offer further guidance.

Encoding Process

Mensural notation was developed in the late thirteenth century in order to more precisely denote rhythm in polyphonic music, and was the notation system that continued to be used to notate music until the sixteenth century. Mensural notation presents particular difficulties for encoding since it is a context-based notation. In other words, whereas the shape of a note and its duration are in a one-to-one relation in notation from the common practice period, this is not the case with mensural notation, where the same note shape can be used in different contexts to denote different durations. Thus the process of encoding mensural music is considerably more complex than encoding Common Practice notation, especially because no currently available music notation software offers the possibility of notating music in scored-up mensural notation. The process that we developed during the course of this project is summarized below.

The transcriptions are taken from a single manuscript source (and thus are diplomatic transcriptions and not editions), and the digital encodings of these transcriptions follow the MEI schema (a core set of rules developed for encoding music notation documents as XML). The MEI schema has a mensural notation module. At present, the encodings of the ‘Measuring Polyphony’ project capture the following notational features:

  • the form of each note (duplex long, breve, semibreve, minim, etc.);
  • the actual duration of each note (whether notes are perfected, imperfected, or altered);
  • rests as notated in the manuscript;
  • the implied mensuration (in some motets this is clearer than in others);
  • ascending and descending plicas added to longs or breves;
  • dots of division and perfection;
  • downward stems on semibreves;
  • staff breaks and page breaks;
  • ligature groupings;
  • the underlaid text (in diplomatic transcription, expanding abbreviations, but without editing or standardising the spellings).

The process we devised to create the encodings is as follows:

  1. The compositions were encoded using the music engraving software, Sibelius. These initial transcriptions were either completed either by the project director directly from the manuscript source, or scanned from a modern scholarly edition, and then corrected in Sibelius and proofread against the edition by the project assistants.
  2. Specific articulation marks were added by the person encoding within the Sibelius transcription that represent specific notational features (view a transcription in the ‘modern’ notation version on our website), as follows: an angular fermata marks a staff end, a round fermata a page end, a staccato dot marks a mensural dot, a tenuto marks a downward stem, a single tremolo marks a descending plica, a double tremolo an ascending plica.
  3. The note values of the transcriptions were then augmented to match as closely as possible the note values of the original notation, i.e., if possible, breves in the mensural notation were recorded as breves in the modern transcription, semibreves as semibreves, etc. However, depending on the original mensuration, dots or ties often had to be used to accurately capture the note relationships. View, for example, on our website the modern notation version of a piece from the Montpellier Codex compared to an ars nova piece like Apollinis/Zodiacum, which has many more dots and ties.
  4. These files were then proofread at least two more times by the project director and assistants against the manuscript source to check the accurate placement of the added articulation marks, and to check the pitches, rhythms, accidentals, etc., and to suggest any editorial accidentals. Any differences between the primary manuscript sources and the transcription are noted in the Commentary. NB - a final proofreading is yet to be completed for some files – this is noted in the Commentary, and we welcome any notifications of inaccuracies in the transcriptions.
  5. These files were then exported into the MEI format (XML-based) using the SibMEI plugin.
  6. Finally, these MEI files were then processed through the CMN-MEI_to_MensuralMEI_Translator script written by Martha Thomae Elias to convert the MEI files into files that conform to the MEI mensural module. The script converts the articulation markings into the appropriate mensural MEI elements and attributes, and converts the modern notation note names and rhythmic durations into the appropriate mensural markup. For the Github repository of this script and more details, see

Website design and features

The encoded transcriptions are presented here online in a scored-up mensural notation via a customization of Verovio, an open-source library for engraving MEI music scores into SVG and which also generates audio playback highlighting the transcription as it plays in real time. The Verovio code library also provides the functionality to download a PDF of the SVG image. For this project, Laurent Pugin, the developer of Verovio, extended the library so that it could display the scored-up transcriptions in black mensural notation, and allow for the highlighted playback of mensural notation in a variety of MIDI instrument formats.

For many of the compositions presented here, digital images of the original manuscripts are available online. In the case of the Roman de Fauvel manuscript (Ms f. fr. 146), the Bibliothèque nationale de France has made its images available through the IIIF framework, and thus those images can be accessed directly through the Measuring Polyphony interface. The image viewer on is the open source Diva.js, developed by Andrew Hankinson. When the manuscript images are not yet available through IIIF, links to the institution’s websites are included here, so that users can view the manuscript images directly on the appropriate institution’s website.

A lightweight web architecture has been employed here. Since the metadata for these compositions is already available through DIAMM, all the necessary metadata about each composition is encoded directly in the meiHead element of the MEI files, and the website built with the open source Jekyll Pages of Github.

Editorial Decisions

Semibreves: In the ars antiqua repertoire, which includes the Fauvel motets, all semibreves (in groups of four or more) encoded simply as semibreves separated by dots of division (although those semibreves notated with a downward stem are specified in the encoding), unless downward stems were added in the manuscript source, if so the semibreve is recorded as longer, usually by tagging it as a major semibreve. Pairs of semibreves are encoded following Franconian conventions of minor, major, unless the first note is marked by a descending stem. Encoding the motets in this way will allows for an eventual flexibility in imposition a mensural interpretation, for example, in those Fauvel motets where it is unclear whether they are in tempus perfectum or imperfectum. One could envision an eventual online edition where a performer could easily switch back and forth between different editorial interpretations of mensuration or rhythmic duration. For now, the groups of semibreves are simply ‘fit’ into the duration of a breve.

Accidentals: Whether indicated in manuscript, or added as editorial suggestions, last for the equivalent of one measure, marked by dashed barlines, in the transcription

Known Issues

Hyphens between text syllables: In the export of the texts from syllables, the placement of hyphens between syllables needs to be corrected. Hyphens are not currently displayed in this iteration of the interface (May 2018).

Ligatures: While ligature groupings, including coniuncturae, were recorded in the Sibelius transcription, Sibelius is primarily an engraving software concerned with the graphic appearance, and in Sibelius the brackets that mark ligatures are not associated properly with specific notes (i.e., they are not specifically attached to the notes at the beginning and ends of the ligature brackets). Thus it is currently tricky to export the ligature markings out from Sibelius to MEI. We are pondering solutions, however (May 2018).

Plicas: Currently Verovio does not display a specific grapheme for notes marked with plicas; these are, however, encoded in the mensural MEI file, and viewable in the code (May 2018).

Ficta: There is a current issue with distinguishing between original and added accidentals (ficta accidentals) in the Sibelius to MEI export. We are in the process of manually correcting the added accidentals, but not all compositions have been updated yet (May 2018).

Future Plans

There are 8 motets for which transcriptions have been made and proofread, however, because of some of their quirky mensuration issues (such as changes of mensuration, or coloration), they currently cannot be transformed accurately with the MEIMensural script, and are only viewable on this site currently in their ‘modern notation’ versions.

These pieces present useful case studies as we begin the next phase of this project, which is to consolidate lessons learned from this project in the creation of a streamlined yet flexible process, which would include the the development of a simple mensural MEI editor, that would allow musicologists to input ars antiqua or ars nova mensural notation directly into an web-based editor, and view, hear, and correct scored-up versions during the actual process of transcription.


One of the primary purposes of this project is as ‘proof-of-concept’ and lessons learned will be applied to the next iteration of this project, to be implemented on a larger scale, with user feedback. Therefore, any responses, with respect to the interface, repertoire chosen, bugs, or ideas for further development are appreciated immensely and can be sent directly to