Johann Christoph Demantius was a German composer, music theorist, writer and poet. He was an exact contemporary of Monteverdi, and represented a transitional phase in German Lutheran music from the polyphonic Renaissance style to the early Baroque. Demantius was a hugely prolific composer, though many of his works have been lost. Stylistically he was a successor to Lassus, who was also working in Germany during the first part of Demantius's life. He wrote most of his music before the Thirty Years' War; it is probable that the hardships of the war, including lack of performing musicians, made it difficult to compose and publish