/ ˌɒrəˈtɔːriəʊ; NAmE ˌɔːrəˈtɔːrioʊ; ˌɑːrə-/ noun
( pl. -os ) a long piece of music for singers and an orchestra , usually based on a story from the Bible
—compare cantata
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WORD ORIGIN
Italian , from ecclesiastical Latin oratorium oratory, from the musical services held in the church of the Oratory of St Philip Neri in Rome, Italy.