How did Palestrina use a cantus firmus in his masses?

Giovanni Pierluigi da Palestrina utilized the cantus firmus—a preexistent melody, often derived from Gregorian chant—as a foundational element in many of his masses.

In his approach, Palestrina typically employed the cantus firmus in the tenor voice, a traditional practice where the melody served as the structural core of the polyphonic texture. Beyond simple placement, he demonstrated significant contrapuntal ingenuity by ornamenting and decorating these solemn melodies, effectively integrating them into the musical fabric so that they became indistinguishable from the other, freely composed parts.12

In some instances, such as his masses based on hymn melodies, he paraphrased the traditional material, often placing it in the highest voice. While he frequently utilized this technique in works like Ecce sacerdos magnus and L’Homme armé, he also explored other compositional methods, such as the parody technique and free-style composition, demonstrating his flexibility and mastery of tonal architecture.23