Nonet can refer to things as well, not always nine people.

Not just people

Think of nonet as a specific collection or group of nine, often matching or related.

Collection or group

In music, nonet implies a specific ensemble of nine players, each with a unique part.

Nonet is often associated with classical and chamber music rather than popular genres.

In literature, a nonet is structured with nine lines, which may vary in length and rhythm.

The lines in a nonet poem often decrease in syllables, creating a funnel effect.