A viola looks like a violin, but it is slightly larger and heavier, and its tone is a bit more mellow. It has 3 of the same strings as the violin (A,D,G) but the 4th string is a lower note (C), rather than a higher note (E) -- it actually has the same strings as a cello, only an octave higher. The music for the viola is in the Key of C, which is different than for the violin.