Oratorios
Bach's oratorios can be considered as expanded cantatas. They were also meant to be performed during church services. Other than in the cantatas, a narrator, the Evangelist, tells a story in the exact Bible wording, soloists and the choir have "roles" such as Mary or "the shepherds", in addition to reflective chorales or commenting arias interspersed with the story. The St Matthew Passion and the St John Passion were intended to be performed on Good Friday, before and after the sermon. The six parts of the Christmas Oratorio were intended to be performed on six feast days of the Christmas season, each part composed as a cantata with an opening chorus (except in Part 2) and a closing chorale.
Read more about this topic: Bach Cantata