A Treatise on Musicians from ?c. 1400: The Tractatulus de differentiis et gradibus cantorum by Arnulf de St Ghislain

The historian John Keegan was one of the first to ask the simple yet searching question: what actually happens in combat? It is well known that English footsoldiers received a charge by French knights at the battle of Agincourt in 1415, but what took place when men and horses collided? Keegan gives his answers in The Face of Battle , and it may be time for musicologists to modulate the sonorous questions that he poses there for their own purposes. What actually happened, for example, when a motet by Johannes Ciconia was performed in northern Italy c 1400? When friends and associates gathered together to hear such music, what was the nature of their various musical aptitudes and interests? Did women participate in the performances? What was the role of instrumentalists? Some of these questions, no doubt, will never find an answer; there are no medieval chronicles devoted to musical gatherings as there are chronicles – and many other writings – devoted to battles like Agincourt. None the less, literary and iconographical sources are among those which may still have something to reveal about ‘the face of performance’ (to coin a phrase after Keegan's own), and the purpose of this article is to examine the contents of one that has been unjustly neglected: the Tractatulus de differentiis et gradibus cantorum by Arnulf de St Ghislain. This brief treatise classifies the kinds of musicians who performed or admired polyphonic music and is therefore quite exceptional among the works loosely classified as medieval music theory.