Final answer:
It is true that Renaissance composers focused on the Ordinary of the Catholic Mass for their musical settings, employing polyphony and achieving a unified liturgical musical structure.
Step-by-step explanation:
Renaissance composers indeed concentrated on the Ordinary of the Catholic Mass for their musical settings, making the statement true. The Ordinary comprises the texts of the Mass that remain the same on most days of the liturgical year, as opposed to the Proper, which changes daily depending on the occasion or feast. Polyphony, which is one of the main characteristics of Renaissance music, was extensively used in these compositions. Composers like Palestrina and Victoria are well-known for their mastery in setting the Ordinary of the Mass to music. These settings represented a unity of musical structure and liturgical purpose during the Renaissance period.