A keyboard includes a frame and a plurality of mass bodies. The mass bodies are arranged in parallel to each other. Each of the mass bodies is pivotally supported to pivot about a pivot fulcrum with respect to the frame. The mass bodies are at least one of a plurality of keys configured to be directly operated, a plurality of interlocking members configured to pivot in conjunction with a corresponding one of the plurality of keys, embedded members in the plurality of keys or embedded members in the plurality of interlocking members. At least some of the mass bodies include notched portions being arranged in order from a pitch, which is equal to or greater than a lowest pitch, to a highest pitch. The notched portions are different from each other in at least one of size, position, or distance from the pivot fulcrum.