Harmonica comprising: - a comb or windchest in the thickness of which are made a plurality of air flow channels, said comb supporting at least one reed plate (3, 4) on which is mounted sound reeds (30, 40) whose oscillations are caused by the flows of air generated by the player through the mouthpiece holes ending in the mouthpiece face of the instrument, - a peripheral shell enabling to hold the harmonica, said shell comprising at least one cover plate (10, 10) for amplifying of the sounds and projecting them towards the bell of the instrument, said harmonica wherein: - each reed plate (3, 4) is sandwiched between the pressing face concerned of the comb and corresponding the cover plate (5, 5), - said cover plate (5, 5) pressing against the external face of the reed plate concerned (3, 4) on the one hand, side mouthpiece of the instrument, via its upper lip pressing all along the upper zone of the reed plate extending in the longitudinal direction of the instrument on the side of the mouthpiece face, and on the other hand on the side of the bell of the instrument via pressing tabs pressing on the external face of the reed plate concerned in zones between the face of the harmonica forming the bell of the instrument and the bottom of the air flow channels supplying the sound reeds, - pressing means for pressing the reed plate concerned against the corresponding face of the comb and said cover plate against the external face of the reed plate concerned, said harmonica being characterized in that: the pressing means are composed of at least one screw inserted in the part of the instrument which is delimited, in the longitudinal direction of the harmonica, by the two planes perpendicular to the average longitudinal plane (Pm) of the instrument, one passing through the longitudinal axis of the air flow channel supplying the most high-pitched reed of the instrument and the other passing through the longitudinal axis of the channel supplying the most low-pitched sound reed of the instrument. - a comb or windchest in the thickness of which are made a plurality of air flow channels, said comb supporting at least one reed plate (3, 4) on which is mounted sound reeds (30, 40) whose oscillations are caused by the flows of air generated by the player through the mouthpiece holes ending in the mouthpiece face of the instrument, - a peripheral shell enabling to hold the harmonica, said shell comprising at least one cover plate (10, 10) for amplifying of the sounds and projecting them towards the bell of the instrument, - each reed plate (3, 4) is sandwiched between the pressing face concerned of the comb and corresponding the cover plate (5, 5), - said cover plate (5, 5) pressing against the external face of the reed plate concerned (3, 4) on the one hand, side mouthpiece of the instrument, via its upper lip pressing all along the upper zone of the reed plate extending in the longitudinal direction of the instrument on the side of the mouthpiece face, and on the other hand on the side of the bell of the instrument via pressing tabs pressing on the external face of the reed plate concerned in zones between the face of the harmonica forming the bell of the instrument and the bottom of the air flow channels supplying the sound reeds, - pressing means for pressing the reed plate concerned against the corresponding face of the comb and said cover plate against the external face of the reed plate concerned, the pressing means are composed of at least one screw inserted in the part of the instrument which is delimited, in the longitudinal direction of the harmonica, by the two planes perpendicular to the average longitudinal plane (Pm) of the instrument, one passing through the longitudinal axis of the air flow channel supplying the most high-pitched reed of the instrument and the other passing through the longitudinal axis of the channel supplying the most low-pitched sound reed of the instrument.