The viola is a string instrument that is bowed or played with varying techniques. It is slightly larger than a violin and has a lower and deeper sound. Since the 18th century it has been the middle or alto voice of the violin family, between the violin (which is tuned a perfect fifth above) and the cello (which is tuned an octave below). The strings from low to high are typically tuned to C3, G3, D4, and A4.
In the past, the viola varied in size and style as did its names. The Italians often used the term: "viola da braccio" meaning literally: 'of the arm'. "Brazzo" was another Italian word referring to the viola which the Germans adopted in the form: "Bratsche". The French had their own names: "Cinquiesme" was a small viola, "Haute Contre" was a large viola, and "Taile" meant "Tenor". In the modern era, the French use the term "Alto", a reference to its range.
The viola had enjoyed popularity in the heyday of five-part harmony up until the eighteenth century, taking three lines of the harmony and occasionally playing the melody line. Music that is written for the viola differs from that of most other instruments in that it primarily uses the alto clef. Viola music switches to the treble clef when there are substantial sections of music written in a higher register to make the notes easier to read.