The purpose of the present invention is to conceive a mouthpiece of a trumpet or similar musical instrument, which would be on the one hand permanently placed onto the musical instrument, and should on the other hand enable alternatively playing either the instrument as such or--when desired--also practicing by means of the so-called buzzing the mouthpiece. The mouthpiece (2) is an axially symmetric tubular part having a connecting end portion (21) adapted for inserting into a connecting portion (10) of a trumpet (1) or similar instrument, as well as a widened and thickened opposite playing end portion (22). A blocking means (3) equipped with a ventilation opening (30) is foreseen on the outward circumferential surface of the said wall (25) of the mouthpiece (2).