OVER the last few years, the Leiden choirbooks have become known to quite a few music lovers in the Netherlands and abroad. Much of the upsurge was due to an ambitious concert and recording project of Peter de Groot and the Egidius Kwartet. From 2010 to 2015, each year they produced a double CD devoted to one of the manuscripts. As some of the pieces that were chosen for the recordings were large-scale compositions, the Egidius Kwartet was complemented with extra singers to create an ensemble – The Egidius Kwartet and College – that was capable of dealing with these extensive works and that, more or less, approached the vocal forces for which the books had been copied in the sixteenth century. The CDs were presented at annual concerts, and promotional materials were prepared, among them a DVD and a nicely illustrated little book. The start of the project coincided with the digitization of the six manuscripts. High-resolution pictures were made of all choirbooks, which are now accessible through the website of the Erfgoed Leiden en Omstreken (which encompasses the former Gemeentearchief Leiden). Whilst working on the extensive liner notes for the CDs and emailing suggestions for upcoming programmes, it occurred to me that this might be a good time to revise my earlier work on the choirbooks and make it available to a wider audience. The present book is the result of my efforts.

It is my pleasure to express my thanks to those without whom this research project, which was funded by the Netherlands Organisation for Scientific Research (NWO), would have been much more complicated. In 1992 I visited the Musicological Archives for Renaissance Manuscript Studies of the University of Illinois at Urbana-Champaign. Herbert Kellman and Timothy Barnes kindly welcomed me and made all facilities available for my study of the Leiden repertoire. A short visit to the Deutsches Musikgeschichtliches Archiv at Kassel in 1993 was particularly fruitful thanks to the efforts of Dr Jurgen Kindermann.

The research project would not have been possible without the help of the then director of the Museum De Lakenhal, drs. H. Bolten-Rempt, and of mr. T.N. Schelhaas, who was director of the municipal archives at the time.