The Alto Clef is a musical notation used primarily for instruments that play in the alto range, such as the viola. It is a C clef, meaning it designates the position of the note C on the staff. In the alto clef, the middle line of the staff represents the note C, allowing musicians to read music more easily for their specific range. This clef is less common than the treble clef and bass clef, but it is essential for certain orchestral and chamber music settings. Composers often use the alto clef to write music that is tailored for instruments like the viola, ensuring that the notes are accessible for performers.