Chapter 2 analyses the core aesthetic of the French ars nova—its subtilitas (subtlety). Through a close reading of two popular fourteenth-century motets that were cited as examples in theory treatises (Tribum/Quoniam, probably written in the late 1310s, and Apta/Flos, of c. 1350), chapter 2 reveals the distinctions that mid-fourteenth-century writers and musicians made between the subtle art of the moderns and the crude or unrefined manner of the older style. They draw on a long history of writings that characterise subtilitas—some sharply negative, some glowingly positive. Probably the best known in the medieval period were the criticisms of John of Salisbury (c. 1120-1180), who inveighed on the logical subtleties practised by his younger contemporaries. Jacobus echoes the moralising tone of John of Salisbury’s rhetoric. The moderni who were the target of Jacobus’s critique appear to have sought out the aesthetic of subtilitas and the novelties that Des Murs’s new methods for notating duration enabled. The moderni explicitly positioned the delicate subtlety of their compositions against the crudity of the ars antiqua.