Ancient Japanese music was influenced by Chinese music which reached Japan in 680 BC. Traditional Japanese musical instruments include the shamisen, koto, and biwa. The shamisen has a hollow body with three silk strings and a long unfretted neck, and may have dogskin or catskin coverings. The koto is a Japanese zither with 13 silk-stretched strings over movable bridges. The biwa is a pear-shaped lute with four strings that plays melody and marks time. While retaining traditions, Japanese music has incorporated Western genres like jazz and chamber music, with precise classical performances and little improvisation.