Henricus de Zeelandia

Henricus de Zeelandia was a music theorist from the southern Netherlands, active in the fourteenth century. Very little is preserved about his life; the only thing known with certainty is that he wrote a brief treatise, the Tractatus de cantu perfecto et imperfecto, which today is known above all for its role as an introduction to another, greater work.

This treatise serves as a preface to the celebrated Libellus cantus mensurabilis of Johannes de Muris, dated to around 1340. It opens with an account of intervals and their classification into consonances and dissonances. It is striking that the diatessaron appears as a dissonance, and that major and minor thirds are regarded as imperfect consonances. It then gives a very condensed summary of a compilation on plainchant according to modern authorities, covering solmisation, mutation and modes. It concludes with some notes on discant: the usual rules for beginning and ending, the choice of intervals, contrary motion, and the prohibition of mi against fa, all with scarcely any explanation.

Its importance is more pedagogical than informative. As a source of data it contributes almost nothing new, but it shows clearly which knowledge was considered indispensable for a beginner, since, according to the text itself, rules, rather than practice, are the foundation of the art. It names only Boethius, although it clearly depends on other authorities, especially Guido of Arezzo.