An oratorio is a large musical composition including an orchestra, a choir, and solo. The oratorio was somewhat modeled after the opera. Their similarities include the use of a choir, soloists, an ensemble, various distinguishable characters, and arias. However, opera is musical theatre, while oratorio is strictly a concert piece, though they are sometimes staged as operas. There is little or no interaction between the characters, no props or elaborate costumes. The most important difference