A dramatic work for soloists, chorus, and orchestra, fairly long and not staged, is called a(n) .

Oratorio

Explanation:

An oratorio is a large musical composition for soloists, chorus, orchestra, instrumentals, and arias which is usually based on a biblical or religious event.

It is a performance in which the story is told by means of its music and not by costumes, pantomime, or aesthetics.

It is different from an opera because while an opera is a musical theatre, an oratorio is a concert piece– even though their roles and uses can be used interchangeably.