The so-called Brussels Rotulus (Ms. 19606 from the Bibliothèque royale de Belgique ) is a medieval source for studying the motet and the musicological era of Ars nova . All ten compositions on the rotulus are motets, except for the first piece on the recto side . Most of the motets cited are also known from other manuscripts and have already been published in modern editions. It is an example of an early form, but almost completely established, notation of the Ars nova. Even if the downward-pointing stem of the note on the semibrevis still marks it as semibrevis major, the minima has already fully established itself.
Even if the repertoire comes mainly from Paris, the illumination points to another place of origin further north.
The rotulus is 17.5 cm wide and 139 cm long and is one of the few remaining rotuli. Such rotuli, which correspond to a rolled-up manuscript, have the advantage that they are not as heavy and large-format as their counterparts (magnificent manuscripts) and can be transported more easily. A disadvantage at the same time is of course that a rotulus is less well protected and, as a commodity, is quickly exposed to wear and tear. Neither disposed of nor used as waste and the Brussels Rotulus has been preserved as an important source.