C clef

A clef that moves

The page Reading music says that the clef at the start of every line fixes which note lies on which line. Besides treble and bass clef there are C clefs, such as the viola clef, which only become important for advanced players. The C clef always marks middle C (C4). Where this C lies on the staff is decided by the line on which the sign sits.

The symbol library describes this in more detail. In the Middle Ages and the Baroque the C clef moved between several lines depending on the voice range; today it is in use almost only as the alto clef for the viola and as the tenor clef for high cello, trombone and bassoon. Soprano and mezzo-soprano clef today mostly occur only in urtext and early-music editions; modern editions generally write such parts in the treble clef.

Why not simply treble or bass clef?

According to the library, the alto clef is used mainly for the viola because its range lies exactly where neither treble nor bass clef would manage without many ledger lines. Middle C lies on the first ledger line below the staff in one clef and on the first above it in the other; in the alto clef it sits in the middle of the staff.

An example from the archive

The archive holds the individual parts of Mozart's serenade. This lets the same movement be compared in different clefs:

One serenade, three clefs

• Eine kleine Nachtmusik, Stimme Viola Wolfgang Amadeus Mozart, K. 525, 1st movement Allegro, Serenade in G major · viola · 2 pages

  The viola part is in the alto clef: the sign sits on the middle line, and one sharp in the key signature shows G major. The lines of the staff here mean completely different notes from those in the treble clef.

• Eine kleine Nachtmusik, Stimme Violine 1 Wolfgang Amadeus Mozart, K. 525, 1st movement Allegro · violin · 2 pages

  For comparison, the same serenade in the treble clef. Here too bar 1 carries the dynamic marking f; the violin lies in a higher range than the viola.

How to adjust to unfamiliar notation is covered in the article Sight-reading. The page Reading music also names the commonest beginner's mistake: overlooking the clef. Anyone who reads the bass clef like a treble clef gets every note wrong. With the C clef this applies all the more: always check the clef first.