Mouthpiece (brass)

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The mouthpiece on brass instruments is the part of the instrument placed on the player's lips. The mouthpiece is a circular opening that is enclosed by a rim and that leads to the instrument via a semi-spherical or conical cavity called the cup. From the cup, a smaller opening (the throat) leads into a tapered cylindrical passage called the backbore. The backbore is housed in a tapered shank, which is inserted into an opening called the receiver on the main body of the instrument.

On all brass instruments, sound is produced when the player's vibrating lips (embouchure) cause the air column, i.e. the air enclosed inside the instrument, to vibrate. This is done by pressing the lips together and blowing air through them in order to produce a 'buzz.' The mouthpiece is where this lip vibration takes place. On most instruments, the mouthpiece can be detached from the main instrument in order to facilitate putting the instrument in its case, to use different mouthpieces with the same instrument, or to 'play' the mouthpiece by itself to exercise the player's embouchure.

Different mouthpieces will produce different qualities of tone when used with the same instrument. Lower instruments also have larger mouthpieces, to maximize resonance (see pitch of brass instruments). Also, mouthpieces are selected to suit the embouchure of the player, to produce a certain timbre, or to optimize the instrument for certain playing styles. For example, trumpet and trombone mouthpieces are usually semi-spherical whereas French horn mouthpieces are conical.