Focusing on the number of performers:
* Solo: A performance by a single person.
* Ensemble: A group of musicians or singers performing together.
* Chorus: A large group of singers performing together.
* Orchestra: A large group of instrumentalists performing together.
Focusing on the type of performance:
* Monologue: A long speech by one person.
* Dialogue: A conversation between two or more people.
* Recitation: The act of reciting something aloud.
Other related terms:
* Unison: When multiple singers or instruments perform the same notes simultaneously.
* Harmony: When multiple voices or instruments blend together in a pleasing way.
The best antonym will depend on the specific context of your sentence.