Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A vocal score or piano-vocal score is a music score of an opera, or a vocal or choral composition with orchestra such as an oratorio or cantata, in which 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.