Viola is a stringed instrument that is often found in an orchestra. While looking similar (Identical to most) to the violin, they are indeed different. Viola has the strings C, G, D, and A (lowest to highest) and plays in alto clef, while violin has the strings G, D, A, and E and plays in treble clef. Viola tends to produce a darker tone than violin. Cello has the same strings as a viola, but their strings are an octave lower than the violas'.