One of the first things one discovers when studying Gregorian paleography is that some neumes (pes, clivis, torculus, porrectus, etc.) are chironomic—that is, they resemble the movement of the conductor’s hand. Other neumatic signs (the oriscus / tilde, trigon, quilisma, strophae) have a symbolic meaning, often borrowed from punctuation or contraction, that does not necessarily depict the shape of the musical gesture.
A challenge for modern conductors is to develop a technique of chironomy that is faithful to the manuscript tradition while still being understood by singers who do not have the same frame of reference as a 9th century cleric. Here’s a little clip of the gradual Requiem aeternam from our recent Day of the Dead concert where I employ a chironomic style influenced by my time singing with the schola at La Sainte Trinité in Paris, Theodore Marier’s take on the Solesmes method with its arsic and thetic ictuses, and a handful of grammar school conducting tricks. The end result resembles no one of these influences in particular, but it does seem to serve the purpose of keeping the ensemble together without beating time.