An adjustable chromatic harmonica incorporating an adjustable mouthpiece where, for each mouth-hole, the player's breath may be selectively connected to one or more available reed cells. This is by means of a rotatable cup-shaped valve, with an opening or port in its side, being mounted in each mouth-hole such that the port can be registered by rotation with one of a group of surrounding air ducts, each of which is connected to one or more reed cells in the body of the harmonica. In some embodiments an apertured slide is interposed between the mouthpiece and the body. In some embodiments devices are provided for rotating the valves in independent groups while the harmonica is being played. In embodiments where each group of mouth-holes can be independently adjusted, a large number of physical states is possible. Consequently, some embodiments have the capability of playing chromatic melodies and several common chord types in all twelve musical keys.