Johannes Nucius (also Nux, Nucis) (c. 1556 – March 25, 1620) was a German composer and music theorist of the late Renaissance and early Baroque eras.
Although isolated from most of the major centers of musical activity, he was a polished composer in the style of Lassus and penned an extremely influential treatise on the rhetorical application of compositional devices.
He rose in the hierarchy at the monastery, becoming a deacon, and later an abbot at Himmelwitz; however in 1598 he turned over most of his duties to his assistants in order to compose and write his musical treatise.
Some of the devices named are: commissura (passing note dissonances), fuga (melodic imitation of varying kinds), repetitio (the repetition of a section for dramatic effect), climax (passages in parallel thirds or tenths), complexio (the reprise of an opening passage at the end to make a cohesive statement), homoioteleuton (the dramatic use of silence by inserting a sudden rest for rhetorical effect) (in this Nucius is one of the first music theorists to recognize the powerful musical use of silence, an idea which was to attain fame in modern times in the work of John Cage), and syncopatio (syncopation, for rhythmic enhancement).
While some of his book is based on previous writings by Heinrich Glarean and Franchinus Gaffurius, the section on the rhetorical devices in music is original, and signifies the rapidly changing practice during the transitional period between Renaissance and Baroque styles.