Final answer:
Claudio Monteverdi was the music director at St. Mark's Cathedral in Venice from 1613 until his death in 1643.
Step-by-step explanation:
The early opera composer Claudio Monteverdi served as the music director at St. Mark's Cathedral in Venice from 1613 until his death in 1643. Monteverdi was a significant figure in the transition from the Renaissance style of music to that of the Baroque period, and his position at St. Mark's Cathedral allowed him to contribute substantially to the development of opera as a genre during the early 17th century.