Rhythmic trees in Bodleian Library MS. Bodley 515: visual metaphor in musical diagrams

In representing, explaining, theorizing and demonstrating ephemeral phenomena, not always aural, in a predominantly text-based (and most-likely silent) form, authors and scribes made widespread use of diagrammatic, illustrative and exemplary content. As such, manuscripts containing musical theory often include a range of non-text materials to communicate ideas, represent musical space and encode sounds onto the silent page. These range from short passages of musical notation placed within the body of a treatise text in a variety of formats, through to diagrammatic constructions occupying entire openings that would not be out of place in arithmetic and architectural writings. Far from being supplemental material, these diagrams and examples are integral to communicating the concepts and principles music theory treatises tried to explain and, ultimately, preserve. In some cases, these materials may be even more important in illuminating contemporaneous conceptualisations of musical ideas than a written text. They offer an insight into not only the key principles but, importantly, the ways these diagrams were understood by musical thinkers, writers and readers. Although wider issues relating to musical exemplarity and diagrammatology extend beyond the scope of this short article, a particularly interesting area in terms of music theory is the representation of rhythm in musical notation. Of key importance here are the ways in which note values could be subdivided and how music theorists chose to explain such phenomena.