The harmonica according to the invention includes a comb or windchest supporting at least one reed plate on which are mounted sound reeds and a peripheral shell allowing to hold the harmonica, said shell including at least one cover plate. Each of its reed plates is sandwiched between the pressing face concerned of the comb and the corresponding cover plate by pressing means for bringing said cover plate closer to the comb between the mouthpiece face of the instrument and the pressing tabs on the side of the bell of the instrument.