In a letter from Pope Saint Gregory I to Leander, Bishop of Seville, the former waxes metaphorically, liberally using the image of a choirmaster conducting from the organ while accompanying the choir. The detail of the description suggests first-hand experience.
“For what is the office of the body other than the organ of the heart?” he wrote. “And however skilled an expert in singing might be, he cannot do justice to his music unless external services are also in harmony with it, because, of course, an organ that is broken does not spring back properly for a song, even when it is conducted by an experienced hand; nor does its wind produce an artistic effect if a pipe is split with cracks and is too shrill.”
“And so, how much more heavily is the quality of my exposition depressed, in which damage to the organ dissipates the charm of my expression, so that no skill gained from experience can compose it?”
This passage seems to reveal Gregory himself as an experienced choirmaster, even conducting solo singers, while using an organ to accompany them. While he may not have been responsible for all the musical achievements legend has attributed to him, his life was filled with opportunities to cultivate musical skills, especially on the organ.
This according to “Gregory the Great: On organ lessons and on equipping monasteries” by John Martyn (Medievalia et humanistica XXX  pp. 107–113).
Gregory the Great’s Papacy began on this day in 590 C.E. Above, a depiction by Jusepe de Ribera; below, the Gregorian chant Salve regina.
The Liber usualis is a valuable resource for musical scholars; as a compendium of the most common chants used by the Catholic Church, it is particularly useful for identifying the origins of chants used in polyphonic compositions.
Using Optical Music Recognition and Optical Text Recognition, Search the Liber usualis presents a scanned, searchable version of this important resource. Published by the Distributed Digital Music Archives & Libraries Lab and sponsored by the Single Interface for Music Score Searching and Analysis (SIMSSA), this is a proof-of-concept demonstration for the larger task of providing search capabilities for all digitized musical works.
Below, a Palm Sunday antiphon with scrolling notation.
In 2012 the Akademia Muzyczna im. Karola Lipińskiego in Wrocław launched the series Psalate synetos with Wybrane zagadnienia akompaniamentu liturgicznego (Selected problems of liturgical accompaniment, ISBN 978-83-86543-69-2), edited by Marta Kierska-Witczak. The series is dedicated to church music and is addressed to organ students and others who wish to widen their scope of knowledge and practical skills.
The first volume combines contemporary church music theory and practice. Its 16 essays are divided into two groups: Chorał gregoriański źródłem odniesień dla nowożytnej muzyki liturgicznej (Gregorian chant as a source of reference for modern liturgical music) and Historyczny, estetyczny oraz praktyczny wymiar akompaniamentu liturgicznego i liturgicznej improwizacji organowej (Historical, aesthetic, and practical aspects of liturgical accompaniment and liturgical organ improvisation). The table of contents is here.