How does the Notre Dame School's music typically differ from earlier sacred works?

The Notre Dame School's music is distinguished by its inclusion of the earliest examples of polyphony, which marks a significant departure from earlier sacred works that were predominantly monophonic. Monophonic music consists of a single melodic line without any harmonic support, which was the norm in the earlier traditions of sacred music, such as Gregorian chant.

Polyphony introduces multiple independent melodies being sung simultaneously, creating a richer and more complex texture. This development in musical style during the 12th century, particularly in the works associated with composers like Léonin and Pérotin at the Notre Dame Cathedral, laid the groundwork for the evolution of Western music. The harmonization and interaction of different melodic lines in polyphonic music allowed for greater emotional expression and sophistication in musical storytelling, enhancing the liturgical experience of worship.

The other options do not accurately represent the contributions of the Notre Dame School. The music certainly did not abandon religious themes, as sacred themes remained central to its composition. Additionally, the focus was on vocal music rather than an exclusive use of instrumental accompaniment, which later became more prominent in other musical genres. Thus, the inclusion of polyphony is what fundamentally defines the Notre Dame School's contributions to music history.