Clefs · Music theory
What a clef is for and how to read the treble, bass, alto and tenor clefs.
What a clef is for
The staff only shows which note is higher or lower; the clef, at the beginning, says which note each one is. Every clef gives its name to one line, and from it the others are read in order, line and space, up and down.
There are three clef signs, G, F and C, and depending on the line they are written on they make different clefs. Each voice or instrument uses the one that keeps its range inside the staff, with as few ledger lines as possible.
From letter to sign
The three clefs are letters that changed shape over the centuries: the treble was a G, the bass, an F and the C clef, a C. The first letter clefs appear in Gregorian chant notation and their current shape settled around 1600.
They keep their original function: to show which line has a given note. That is why one clef can be written on different lines, and why the C clef has several positions.