Bach's St Matthew Passion is almost always described as a double-choir composition for two choirs and two orchestras. Two large ensembles play in dialogue, and the score presents a symmetrical structure. The scoring of the two groups of singers and players is identical, and each ensemble has four soloists for the arias. On the stage one often sees two equal groups of singers, and an orchestra likewise divided exactly into two. The Evangelist and Jesus are often the only exceptions to this impressive symmetry.