 to show the vocal parts (solo and choral) on their staves and the orchestral parts in a piano reduction (usually for two hands) underneath the vocal parts; the purely orchestral sections of the score are also reduced for piano.If a portion of the work is "a cappella", a piano reduction of the vocal parts is often added to aid in rehearsal (this often is the case with "a cappella" religious sheet music).Piano-vocal scores serve as a convenient way for vocal soloists and choristers to learn the music and rehearse separately from the orchestra.