Guatemalan Digitization Project
This a Music Information Retrieval (MIR) project involving three big steps, each related to a different type of technology. The goal of the project is to be able to retrieve digital scores with the voices properly lined-up from Renaissance polyphonic books. Renaissance polyphony is notated in:
- Mensural notation. This is an early music notation system where the duration of notes depends on the mensuration (meter), the note shape, and—when dealing with triple-meter pieces—the context (i.e., notes preceding or following).
- Separate parts. The voices are contained in different areas of the book opening (e.g., choirbook format) or on completely different books (e.g., partbooks).
In this project, a mensural music source (Guatemala City’s Metropolitan Cathedral polyphonic choirbook 1) is digitized, and then processed by different MIR technologies to convert the separate-parts layout of the voices into a score with the voices properly lined up—dealing with the intricacies of mensural notation regarding rhythmic interpretation, as well as correcting scribal errors.
The pipeline, and technologies behind the scene of each of the three steps are shown in the diagram below:
The first step (shown in green in the diagram) is digitization, which—given the lack of suitable digitization options in Guatemala—was conducted with a do-it-yourself (DIY) book scanner. Click here for details!
The next two steps are the MIR steps, which allow to semiautomatically transcribe the images of mensural sources into symbolic scores (as indicated by the orange steps in the diagdram).
The first of these orange steps is the optical music recognition (OMR) step. This OMR step was conducted with MuRET. Similar to OCR (optical character recognition) automatically recognizes the characters of digital text document, OMR (optical music recognition) automatically recognizes the music symbols in a digital music document. MuRET is an OMR framework that has support for the recognition of handwritten mensural notation (among other things), and it allows also to correct the results of this recognition process in case of errors.
Since we are dealing with mensural notation, however, recognizing the music symbols is not enough to retrieve all the rhythmic information of these symbols and line up the voices into a score. An extra step is needed, this is the automatic scoring up and editorial correction step (the last orange step in the diagram). This step is performed by the Measuring Polyphony (MP) Editor, which automatically scores up the piece (as it interprets mensural notation with a heuristic method I introduced in The Mensural Scoring-Up Tool paper) and allows for performing editorial corrections (corrections of scribal errors) that can solve alignment issues. The detection of scribal errors is facilitated by the MP Editor’s barring and switch to modern clefs functionalities, and by highlighting of “illegal dissonances.” This marking of illegal dissonances is conducted by the Dissonance Filter (DF) that is part of the humlib library. The DF is integrated into the MP Editor, it marks all the dissonances in the piece using the labels provided in this table. The ones that are considered “legal” (e.g., passing tones P/p, neighbour tones N/n, suspensions S/s and their agents G/g) are marked in blue font, while the ones considered “illegal” (e.g., unknown dissonances z, unknown dissonances in parallel accompaniment L/l, and dissonant note against known dissonance types Y/y).
The work that allows to use the output of MuRET as input to the MP Editor and the work that allows to use the DF Filter in the MP Editor is contained in the last two sections of this paper. I conducted some testing of the efficiency of using the DF filter to help catching and correcting scribal errors in an automatically scored-up piece within the MP Editor, the experiment and results can be consulted in this paper and summarized in this poster and video.
Summary of the Complete Work
The Corpus: The GCA-Gaha 1 Choirbook
This choirbook has a few sigla associated to it:
- GuatC 1, according to the Census Catalogue.
- GCA-Gc 1, according to the Digital Image Archive of Medieval Music (DIAMM) — Link to entry GCA-Gc 1 in DIAMM
- GCA-Gaha 1, which would be its correct siglum given its current location at the Archivo Histórico Arquidiocesano “Francisco de Paula García Peláez”, Ciudad de Guatemala (GCA-Gaha, according to RISM) — Link to entry GCA-Gaha in RISM.
The choirbook is a Book of Masses. It contains twelve masses: six of them copied from another book (a Libro de Kyries copied by Gaspar Fernandes in 1602), and the other six were added by Manuel José de Quirós in the eighteenth century. It also includes fifteen short pieces, which consists of polyphonic settings of chants (e.g., Asperges me and Vidi aquam).
The following two images show the title page, which indicate that this book was copied from a previous one copied by Gaspar Fernandes in 1602 and to which six new masses were added by Manuel Joseph de Quirós in 176[0], and the index page, which lists the twelve masses according to these two groups (the ones from the 1602 book and the one sadded later).
Virtual Exhibition & Inventory
In the next section, you will find the inventory list of all the pieces in the choirbook. This inventory includes links to mass movements (or work sections) that, when clicked on, will open the corresponding movement (or section) in mei-friend, where the user will be able to:
- Visualize the transcription of the piece, with notes in green for editorial corrections;
- Visualize the original images (we will call these facsimile from now on);
- Explore the piece thanks to the link that exists between the transcription, encoding, and facsimile. Just click on the border of the bounding boxes of the systems/staffs in the facsimile (so it is highlighted in blue), and you will be conducted to the first note/rest of that system in the transcription (which will now be highlighted in blue as well) and to its place in the encoded file (highlighted in orange). You can see this in the following figure.
- Play back the music using the speaker button in the lower-left corner.
Important note: Please make sure that you are using Chrome or Firefox, mei-friend does not work well with Safari.
The transcriptions were fully revised by Ellis Reyes (PhD Candidate in Musicology, McGill University). He proofread the whole symbolic corpus, visualizing and listening to it using mei-friend, making any corrections necessary and adding the ficta. The metadata of each file shows the names of the people (and software) involved in its creation, usually including the names of: Martha Eladia Thomae Elias (mine), Ellis Reyes (proofreader of the whole corpus and in charge of ficta accidentals), Geneviève Gates-Panneton (when involved), and ocasionally Julie E. Cumming and Peter Schubert (who acted as consultants in a few instances).
Inventory List
Here is the list inventoring the contents of the GCA-Gaha 1 (the composer attribution was provided by Guatemalan Musicologist Omar Morales Abril). Click on the links to open the pieces in mei-friend, where you will have access to a kind of “virtual exhibition” showing the transcriptions, with editorial corrections in green; the original images; the link between the transcription, images, and encoding; and playback, just as explained in the previous paragraph. Click on the links! Have a look!
1. Asperges me - [Pedro Bermúdez?]
Added in the 18th century.
2. Asperges me - Anonymous
Added in the 18th century.
3. Vidi aquam - Pedro Bermúdez
Added in the 18th century.
4. Vidi aquam - [Hernando Franco]
Added in the 18th century.
5. Asperges me - [Alonso Trujillo]
Added in the 18th century.
6. Missa sobre las voces - Cristóbal de Morales
From the 1602 Libro de Kyries, copied by Gaspar Fernández. This is Morales’s hexachord mass, which, according to Robert Snow (1996, p. 19), is preserved in only three other sources: a manuscript at the Capilla Real in Granada, the manuscript formerly known as Medinaceli 607 and now owned by Bartolomé March Servera, and Tarazona 5.
7. Missa sine nomine - Giovanni Pierluigi da Palestrina
From the 1602 Libro de Kyries, copied by Gaspar Fernández. This is the Missa sine nomine first published in the compsoer’s Missarum liber secundus in 1567 (RIMS P 660), see Snow (1996, p.19).
8. Missa Pere de nous - Pierre Colin
From the 1602 Libro de Kyries, copied by Gaspar Fernández. This is Colin’s Missa Pere de nous, published at Lyon in 1546 by Jacques Moderne in his Liturgicon musicarum duodecim missarum (RISM C 3310), see Snow (1996, p.19).
9. Missa de 3er tono - Rodrigo de Ceballos
From the 1602 Libro de Kyries, copied by Gaspar Fernández. This is Ceballos’s popular Missa tertii toni, preserved in at least ten other sources (Snow 1996, p.19).
10. Missa sine nomine - José de Torres y Martínez Bravo
Added in the 18th century.
11. Missa O quam gloriosum - Tomás Luis de Victoria
Added in the 18th century. Many concordant European sources.
12. Missa Ave maris stella - Tomás Luis de Victoria
Added in the 18th century. Many concordant European sources.
13. Missa de 5to tono - Luis Serra
Added in the 18th century.
14. Missa de 4to tono - Alegre
Added in the 18th century.
15. Missa de 8to tono - Rodrigo de Ceballos
From the 1602 Libro de Kyries, copied by Gaspar Fernández. This is Ceballos’s Missa Simile est regnum caelorum, a parody mass based on a motet by Morales (Snow 1996, p.19).
16. Missa de Bomba - Pedro Bermúdez
From the 1602 Libro de Kyries, copied by Gaspar Fernández. Parody mass based on Mateo Felcha’s (el Viejo) ensalada la Bomba.
17. Missa sine nomine - Juan Matías de Rivera
Added in the 18th century.
18. Christus natus est - Pedro Bermúdez
Added in the 18th century.
19. Christus natus est - Pedro Bermúdez
Added in the 18th century.
20. Christus natus est - Anonymous
Added in the 18th century.
21. Surrexit Dominus vere - Anonymous
Added in the 18th century.
22. Lumen ad revelationem - Hernando Franco
Added in the 18th century.
23. Lumen ad revelationem - Pedro Bermúdez
Added in the 18th century.
24. Lumen ad revelationem - Pedro Bermúdez
Added in the 18th century.
25. Surrexit Dominus vere - Anonymous
Added in the 18th century.
26. Victimae paschali laudes - Francisco Guerrero
Added in the 18th century.
27. Tantum ergo - [Pedro Bermúdez]
Added in the 18th century.
The original files can be found at the GuatC1 GitHub repository - main branch.
(There is also a secondary branch to visualize all the intermediate files obtained through OMR and the MP Editor, called all_data_omr_and_mped, but it is linked through the main branch’s README.)
Acknowledgements
🇬🇹 Guatemalan Institutions and Colleagues
I am very thankful to the many Guatemalan conservators, archivists, musicologists, photographers, and conservation and archival institutions that supported this project, especially during the digitization stage. I would not have been able to complete this initial phase of the project without the valuable support of:
The Centro de Rescate, Estudios y Análisis Científico del Arte (CREA), a non-profit institution dedicated to the conservation and restoration of historical and cultural movable heritage (i.e., sculptures, paintings, and paper). Its conservators evaluated the condition of the choirbooks, which helped determine the book selected for this pilot project, and provided conservation treatment prior to digitization. I also thank the Fundación Rozas-Botrán, which manages social development projects in health and culture in Central America and Panama and of which CREA is a part.
- Lucy González Muñoz, CREA’s lead conservator, who enthusiastically took on the project, and the two Gabys, who carried out the conservation treatment of the book prior to digitization.
- Thelma Castillo, Art and Culture consultant at the Rozas-Botrán Foundation, who put me in contact with CREA.
The Archivo Histórico Arquidiocesano de Guatemala (AHAG), the archive holding these Cathedral choirbooks and which allowed me to conduct this pilot project.
- Father Eddy René Calvillo, Chancellor of the Ecclesiastical Curia of Santiago de Guatemala and Director of the AHAG, for approving the project.
- Alejandro Conde, archivist, for his advice and support throughout the process.
The Centro de Investigaciones Regionales de Mesoamérica (CIRMA), which holds microfilms of many of the AHAG’s music holdings. Special thanks to:
- Guisela Asensio Lueg, CIRMA’s General Director, who provided me with the contact of the photographer hired for the project.
- Thelma Porres Morfín, Director of CIRMA’s Historical Archive, who showed me the microfilms and provided valuable background information.
- María de los Ángeles Ávila de León, Photo Library Assistant, who generously offered her help during the digitization process.
I extend my gratitude towards:
- Omar Morales Abril, musicologist, for his advice throughout the project and for providing the metadata (especially composer attributions) for the selected choirbook.
- Daniel Hernández-Salazar (artistic photographer), the professional photographer hired for this project. He assisted in setting up the camera and equipment during the first session and provided valuable guidance (e.g., including the verso number directly in the photograph using printed labels placed beside the color patch). As there was no digitization technician specialized in handling special collections, the manuscript handling and digitization were carried out by me under the guidance of several institutions listed below.
- José German Thomae Villela (father), for designing and constructing the book cradle according to the requirements provided.
📷 Digitization Part (External Institutions)
I also thank the experts who provided advice before and during the digitization process. I received support from specialists at three institutions working on digitization projects involving special collections, cultural heritage materials, and music manuscripts:
The McGill Library’s Digital Initiatives.
- Gregory Houston, McGill’s New Media & Digitization Administrator, for his recommendations as to where to obtain archival supplies (e.g., snake weights) and suggestions for future improvements to the book scanner.
The Bibliothèque et Archives nationales du Québec (BAnQ). Special thanks to three BAnQ experts who received me on multiple occasions for consultation on conservation and digitization matters:
- Jessica Régimbald, conservator at the direction du dépôt légal et de la conservation des collections patrimoniales, who advised me on safe manuscript handling, conservation treatments prior to digitization, and the use of platens.
- Marie-Chantal Anctil, coordinator of the section de la reproduction et des ateliers audiovisuels and direction de la numérisation, who advised me on key considerations for building a do-it-yourself (DIY) book scanner.
- Michel Legendre, photographer (direction de la numérisation and section de la reproduction), who advised me on lighting and approved the selected equipment.
Anctil and Legendre also proposed the open-at-one-side cradle configuration (to solve the issue of keeping the page flat without a platen), which I ultimately adopted.
The Digital Image Archive of Medieval Music (DIAMM). Special thanks to:
- Julia Craig-McFeely, Project Manager.
- Lynda Sayce, Lead Photographer.
For their extensive email support throughout the project. Many aspects of the digitization process were based on their advice, including the use of a neutral background, the positioning of the color patch, and the decision not to use a platen.
Finally, thanks to Professor Eun Park and colleagues from the Preservation Management course (McGill). Through this course, I gained valuable knowledge and connected with professionals at BAnQ and McGill Library. I am also grateful to my classmates, for their advice and encouragement.
🔎 MIR Part
I am thankful to everyone involved in the development of MuRET, the software used for the optical music recognition (OMR) component. Special thanks to:
- David Rizo, lead developer of MuRET
- Jorge Calvo-Zaragoza and Antonio Ríos-Vila, for the symbol recognition models
- Francisco (Paco) Castellanos, for the document analysis model
- José Manuel Iñesta, principal investigator of the HISPAMUS project
I also thank to them for their collegial support and collaboration.
Regarding the scoring up stage carried out in the Measuring Polyphony (MP) Editor, I would like to thank:
- Karen Desmond (PI), for supporting the interoperability between MuRET and the MP Editor
- Juliette Regimbal (lead developer), for her help in implementing this interoperability.
- Craig Sapp, for enabling the integration of the humlib dissonant filter
- Alex Morgan, developer of the humlib dissonant filter
I also acknowledge the developers of mei-friend (David Weigl and Werner Goebl), Verovio (Laurent Pugin), and the MEI Community, without whom this work would not have been possible. Special thanks to Werner Goebl for resolving an issue with the facsimile view of mensural voices distributed across the book opening, and to Anna Plaksin for her work on editorial markup display.
✍️ Editorial Correction and Final Corpus
- Geneviève Gates-Panneton, for experimenting with the dissonant filter in the MP Editor
- Ellis Reyes, for proofreading the transcriptions of the entire corpus and making editorial decisions regarding ficta.
- Peter Schubert and Julie E. Cumming, for their advice on problematic passages
🔥 Supporters
Supervisors Julie E. Cumming and Ichiro Fujinaga, for their invaluable guidance, and the Fonds de recherche du Québec – Société et culture (FRQSC), doctoral grant (2019-B2Z-261749) for funding this project.
I also acknowledge the valuable contributions of: Virginia Golcher, Ana Miriam López, Karla Lou, Anneliese Thomae, Emilio Rós Fábregas, Andrés Lou, Juan Pablo Pira Martínez, and Ana Patricia Elías López de Thomae, who supported me in various ways, ranging from sharing knowledge on conservation and musicological research in Guatemala to assisting with filming the digitization process.