How did Palestrina paraphrase plainchant in his sacred music?

In the context of Renaissance counterpoint, Giovanni Pierluigi da Palestrina utilized paraphrase to integrate traditional plainchant into his sacred compositions with great artistry.

Rather than using a chant melody strictly as a static cantus firmus, Palestrina often ornamented and decorated the melody, making it an integral part of the musical texture. In his hymns, he typically paraphrased the traditional melody in the highest voice. His approach involved:1

• Melodic Elaboration: He would alter the original chant by adding notes or changing rhythms, sometimes making the source material nearly indistinguishable from the surrounding freely composed parts.1
• Integration: He treated the chant as a foundational element that could be woven into the polyphonic fabric, ensuring it functioned cohesively within the work's tonal architecture.12
• Artistic Flexibility: While he occasionally used the older cantus firmus technique, his paraphrasing allowed for a more fluid and expressive application of liturgical melodies in his masses and motets.1

This technique reflects his mastery of balancing traditional liturgical material with the sophisticated, imitative polyphony that defined his style.12