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A vocal score or piano-vocal score is a music score of an opera, or a vocal or choral composition written for orchestral accompaniment, such as an oratorio or cantata. In a piano-vocal score, the vocal parts are written out in full, but the accompaniment is reduced and adapted for keyboard (usually piano). The music is usually reduced to two staves; however, more staves, a second keyboardist (piano-four-hands), or a second keyboard part can be added, as needed.
There are two main types of piano-vocal scores. The first kind consists of those scores created by a composer in the process of composing, usually as a harmonic map or "sketch" of the piece to be later orchestrated. The second category includes scores that are arrangements or transcriptions made after the completion of the work, usually by someone other than the composer.
Piano-vocal scores are generally created to enable a conductor or choir leader to rehearse the singers with a piano accompanist before the choir begins rehearsals with the orchestra. The cost of rehearsing with a professional orchestra is so high that choirs typically hold a number of rehearsals with piano accompaniment to prepare the choir, as the cost of hiring a single piano accompanist is much lower than hiring 50-100 orchestral musicians.
Piano-vocal scores are also used by music students, singers and conductors to study the compositional structure of the score. Before the widespread availability of sound recordings, piano-vocal scores were also sold for amateur home performance or small-scale professional performance of the piece, where a full orchestra would not be feasible from an economic or performance space perspective.