Complex sentence: Through the proposition of the dominance of word in his music, Monteverdi achieved threading humanistic themes in his music, which served as a signal that the decorative allegorical style was of no interest to the composer.
Split into simpler sentences: Through the proposition of the dominance of word in his music, Monteverdi threaded humanistic themes throughout his work. This served as a signal that the decorative allegorical style was of no interest to the composer.