A symbol on a musical staff is known as a CLEF. A CLEF is used to indicate the pitch of written notes on a staff, and is usually placed at the beginning of a line of music. The most common clefs are the treble CLEF, bass CLEF, and alto CLEF. The treble CLEF is used for higher pitched instruments such as the violin, while the bass CLEF is used for lower pitched instruments such as the cello. The alto CLEF is used for instruments in the middle range, such as the viola.