Clef

A clef (from the French word for "key") is a symbol in music notation that tells you which notes correspond to the lines and spaces on a staff. When you place a clef on a staff, it assigns a specific pitch to one of the five lines or four spaces, and that determines the pitches for all the other lines and spaces. In modern music, there are three clef symbols: the G-clef, the F-clef, and the C-clef.

Putting a G-clef on a line fixes the G above middle C to that line. An F-clef fixes the F below middle C, and a C-clef fixes middle C itself. Today, the G-clef is most often seen as the treble clef, which places G4 on the second line of the staff. The F-clef is most common as the bass clef, placing F3 on the fourth line. The C-clef mainly appears as the alto clef (middle C on the third line) or the tenor clef (middle C on the fourth line). While a clef can be placed on a space instead of a line, this is rare.

Different clefs let you write music for any instrument or voice, no matter their range. By using the right clef, each part fits comfortably on a staff with few ledger lines. High parts use the G-clef, middle parts use the C-clef, and low parts use the F-clef. Transposing instruments are an exception—they often keep the same clef across an entire family, even if their actual sound is different. For example, all saxophones, even the low ones, read in treble clef.

There is a symmetry around middle C with these clefs. The C-clef defines middle C, while the G-clef and F-clef define notes a fifth above and a fifth below middle C, respectively. Common mnemonics for treble clef notes are "Every Good Boy Does Fine" for the lines and "F A C E" for the spaces. For bass clef, "Good Boys Do Fine Always" works for the lines, and "All Cows Eat Grass" for the spaces.

Theoretically, any clef can go on any line. With five lines and three clefs, there are fifteen possible placements. Six of these are redundant because they give the same note assignments—for instance, a G-clef on the third line matches a C-clef on the bottom line. That leaves nine distinct clefs when limited to lines. Historically, all have been used: the G-clef on the two bottom lines, the F-clef on the three top lines, and the C-clef on the four bottom lines. The C-clef on the topmost line also appeared, but it is equivalent to the F-clef on the third line, making ten historically attested line clefs. Additionally, the C-clef has been used on the third space (not on a line), which matches the more common suboctave treble clef. These ten line clefs (two of which are equivalent) have different names based on the vocal or instrumental range they suit best.

In modern music, only four clefs are regularly used: treble, bass, alto, and tenor. Treble and bass are by far the most common. The tenor clef is used for the upper register of instruments that usually read bass clef, such as cello, bassoon, and trombone. The alto clef is most famously used by the viola. Music for instruments and voices that transpose at the octave is usually written at the transposed pitch, but sometimes appears at concert pitch using an octave clef.

The only G-clef still in common use is the treble clef, with the symbol on the second line. It is the most common clef and often the first one students learn, so "G-clef" and "treble clef" are frequently used interchangeably. Historically, it marked a treble, or pre-pubescent, voice part. Instruments using treble clef include violin, flute, oboe, cor anglais, all clarinets, all saxophones, horn, trumpet, cornet, vibraphone, xylophone, mandolin, recorder, bagpipe, and guitar. Euphonium and baritone horn are sometimes treated as transposing instruments (using treble clef and sounding a major ninth lower) and sometimes as concert-pitch instruments using bass clef. The treble clef is also the upper staff in the grand staff for harp and keyboard instruments. High parts for bass-clef instruments like cello, double bass, bassoon, and trombone are usually written in tenor clef, but very high pitches may use treble clef. The viola may also use treble clef for very high notes. Treble clef is used for soprano, mezzo-soprano, alto, contralto, and tenor voices. Tenor voice parts sound an octave lower and are often written with an octave clef or a double-treble clef.

A G-clef on the first line is called the French clef, or French violin clef. It was used in France in the seventeenth and eighteenth centuries for violin and flute music. It places notes in the same staff positions as the bass clef, but two octaves higher.

When the F-clef is placed on the third line, it is called the baritone clef. This clef was used for the left hand of keyboard music (especially in France, as in the Bauyn manuscript) and for baritone vocal parts. A C-clef on the fifth line gives the same notes as the baritone clef, but this variant is rare.

The only F-clef still in common use is the bass clef, with the clef on the fourth line. Because it is the only F-clef commonly seen, "F-clef" and "bass clef" are often treated as synonyms. Bass clef is used for cello, double bass, and bass guitar.