Magister Jacobus de Ispania, Author of the Speculum musicae

The Speculum musicae of the early fourteenth century, with nearly half a million words, is by a long way the largest medieval treatise on music, and probably the most learned. Only the final two books are about music as commonly understood: the other five invite further work by students of scholastic philosophy, theology and mathematics. For nearly a century, its author has been known as Jacques de Liège or Jacobus Leodiensis. ’Jacobus’ is certain, fixed by an acrostic declared within the text;