JOHANNES DE GROCHEO1 holds a pre-eminent place in the history of medieval music. Throughout the present century, his treatise, and in particular the section dealing with secular monophonic forms (which he calls musica vulgaris), has, perhaps, been cited more than any other work of music theory of the Middle Ages. I might here refer to just a few of the approving opinions expressed in recent decades as an indication of the generally favourable response that his work has evoked not only among musicologists but also among literary historians: De Witt cites his unique place in music history; Stockmann his originality, his practicality, his authoritative pronouncements; and Page his liberal opinions.2 Of course there have been dissenting voices: Gennrich deemed Grocheo's statements unreliable.3 Van der Werf, too, is rather sceptical about the reliability of Grocheo's pronouncements.4 His unfavourable judgement in turn provoked a vigorous defence. De Witt considers that Grocheo's contradictions can be explained by his use of symbolism or our lack of sympathy for medieval attitudes, while Stockmann thinks that Van der Werf completely devalued in an unreasonable manner the entire work of this important theorist, having merely seized on single statements without trying to understand the work as a whole.5 Mandrell also contests Van der Werf's estimation of Grocheo's work and judges it to be a practical treatise.6 Yet even Grocheo's champions feel obliged to qualify their praise: De Witt opines that '... one suspects that Grocheio may have simplified reality in order to reduce it to a rule'; and Stockmann, ever lavish in her praise of this unquestionably unique treatise, admits its ambiguity.7 The high esteem that Grocheo's treatise has generally enjoyed in this century is in marked contrast to that in which it was apparently held in his own time and in the