Abstract: A keyboard instrument for the natural tone system with at least one keyboard whose keys are assigned to the overtones in a predetermined sequence. According to the invention, the keyboard is optimally adapted to the conditions of the natural tone system by the fact that 16 keys are provided per octave which are arranged and constructed in such a way that the natural tones can be played in sequence on three playing levels. One peculiarity of the invention consists of the boxed arrangement of the keys on the three playing levels, whereby only the "harmonic keys" are arranged on the frontal playing level, the "melodic keys" and the tapered "harmonic keys" are arranged on the central playing level, and that the tapered section of the "melodic keys," a further tapered section of the "harmonic keys" and the "chromatic keys" are arranged on the rear playing level. The adjacent key sections on each playing level are equally wide.