The part of a wind instrument that is placed in, on, or by the performer's mouth.<br><br>The part of the brass instrument against which the player's lips are placed. The size and shape of the `cup' or mouthpiece cavity are important determinants of the instrument's intonation, tone quality, and ease of sound production. Mouthpieces for all except some signalling instruments and the mute cornett are detachable and, to some extent, interchangeable between instruments. See also parts of a typical mouthpiece: Backbore, Bite, Cup, Grain, Impression, Rim, Shank, Throat See also parameters used in measuring mouthpieces: Cup depth, Cup diameter, Cup shape, Cup volume, Minimum bore, Minimum shank external diameter, Rim curvature, Rim thickness, Taper angle, Taper depth,