A New Source for the Performance of Cantus Planus and Cantus Fractus in Eighteenth-Century Venice JOSEPH DYER In memoriam H. C. Robbins Landon (1926–2009) The manuscript at the center of this article came into the possession of Boston University as part of the legacy of scores, manuscripts, and books bequeathed to the University by the pre- eminent Haydn scholar and alumnus, Howard Chandler Robbins Land- on. It now resides in the Howard Gotlieb Archival Research Center at Boston University (H. C. Robbins Landon, no. 1419). 1 The repertoire of the manuscript consists primarily of Ordinary chants, divided between plainsong melodies and pieces in cantus fractus (canto fratto). 2 Both for its repertoire and for the insight it offers about the performance of plainsong and cantus fractus in an Italian, possibly Venetian, convent 1 My thanks to Ryan Hendrickson, assistant director for manuscripts, for facilitating my study of this manuscript and providing the images published with this study. A brief introduction was published as ‘‘A Newly Discovered Source of Ordinary Chants in Cantus Planus and Cantus Fractus: A Preliminary Report,’’ in Cantus Planus: Papers Read at the Sixteenth Meeting of the IMS Study Group—Vienna, 2011, August 21–27, ed. Robert Klugseder et al. (Vienna, 2012), 121–26. 2 I use ‘‘plainsong’’ interchangeably with ‘‘canto fermo.’’ The expression ‘‘canto gregoriano’’ is rare in the works of theorists whom I have consulted, though it is employed by Lazaro Venanzio Belli in his Dissertazione sopra li preggi del Canto gregoriano e la necessita ` che hanno gli Ecclesiastici di saperlo (Frascati: Stamperia del Seminario, 1788). 569 The Journal of Musicology, Vol. 33, Issue 4, pp. 569–607, ISSN 0277-9269, electronic ISSN 1533-8347.  2016 by The Regents of the University of California. All rights reserved. Please direct all requests for permis- sion to photocopy or reproduce article content through the University of California Press’s Reprints and Permissions web page, www.ucpress.edu/journals.php?p=reprints. DOI: 10.1525/JM.2016.33.4.569