A staff (or stave, in British English) of written music generally begins with a clef, which indicates the position of one particular note on the staff. The treble clef or G clef was originally a letter G and it identifies the second line up on the five line staff as the note G above middle C. The bass clef or F clef shows the position of the note F below middle C. While the treble and bass clef are the most widely used clefs, other clefs are used, such as the alto clef (used for viola and alto trombone music) and the tenor clef (used for some cello, tenor trombone, and double bass music). Notes representing a pitch outside of the scope of the five line staff can be represented using ledger lines, which provide a single note with additional lines and spaces. Some instruments use mainly one clef, such as violin and flute, which use treble clef and double bass and tuba, which use bass clef. Some instruments regularly use both clefs, such as piano and pipe organ.