Gioseffo Zarlino (1517-1590) was an influential Italian music theorist, composer, and music educator of the Renaissance period. He is best known for his contributions to music theory, particularly in the areas of harmony and counterpoint. Zarlino's most notable works include "Le Istitutioni Harmoniche" (1558), which systematized the rules of counterpoint and harmony, and "Dimostrationi Harmoniche" (1571), which further elaborated on his theories. Zarlino was a key figure in the transition from the modal system to the tonal system that characterized later Western music. His writings laid the groundwork for future theorists and composers, influencing the development of music in both the Renaissance and Baroque periods. His emphasis on the importance of consonance and dissonance in music composition significantly impacted the way music was understood and created in subsequent centuries.