 Mensural notation had developed by fits and starts during the 13th century as the old ligatures/rhythmic modes became, for various reasons, less suited to the indication of polyphony’s new subtleties, as we shall see below.Not the least problem was that notation in individual part-books was cheaper than notation in score (since each piece took up much less overall space), so a way had to be found of doing it—this would involve the development of a reliable system by which to indicate note-by-note metrical value.The beginning of such a solution was Franconian notation, so called after the theorist Franco of Cologne, who outlined the system in his c. 1260 treatise, "Ars cantus mensurabilis" (The art of mensurable music).