The term TYPE OF CLEF refers to the different types of clefs used in music notation. The two most common clefs are the BASS clef, which is also known as the F clef, and the ALTO clef, which is also known as the C clef. The BASS clef is used to notate lower-pitched instruments such as the BASS guitar, double BASS, and cello, while the ALTO clef is used to notate higher-pitched instruments such as the viola and violin. Both clefs are represented by four letters: BASS and ALTO.