clef

Clef is a musical symbol placed at the left end of a staff that assigns a specific pitch to one of the staff's lines. By defining which line represents, for example, G, C, or F, a clef determines the usable pitch range for the notes written on the staff and minimizes the need for ledger lines.

The most common clefs in modern notation are the treble (G) clef and the bass (F) clef. The treble clef circles the second line, indicating that that line is G above middle C. The bass clef marks the fourth line as F below middle C. Less common today, the C-clefs place middle C on a designated line: the alto clef on the third line, the tenor clef on the fourth line, and the soprano and mezzo-soprano clefs on the first and second lines respectively. These are used for viola, cello, bassoon, and certain vocal and early instrumental parts.

Historically, clefs evolved with the five-line staff developed in medieval and Renaissance notation. The C-clefs were introduced to provide alternative reference points, allowing instruments with wide ranges to read comfortably. In modern scores, clefs are often changed within a piece to avoid excessive ledger lines and to accommodate different instruments or voices. The clef itself does not transpose pitches; it simply affects how written notes map to actual pitches, while transposition for an instrument is indicated separately by its music notation.

Etymology: clef derives from Latin clavis "key" through Old French clef, reflecting its function as the "key" to reading the staff.