Cross-section of a mouthpiece
The mouthpiece has more of an effect on the sound of the clarinet than anything else, so finding the right one (or at least two for an advanced player) is important. The best way to do this is to try out a number of different mouthpieces in order to find the best that suits you. Mouthpieces sound different from one another due to lots of factors including the size of the tip opening - on a Bb clarinet mouthpiece this can be from about 0.5mm or less to approximately 1.3mm, and the length of the lay (between the tip opening to where the reed and mouthpiece meet) which can be from 9mm to 25.5mm. Also important are the thickness of the side and tip rails (thinner rails are preferable) and the shape of the chamber (the baffle, side walls and throat). Many players feel that a close tip opening (approximately 0.7mm) and a long lay (19-20mm) produce a varied and colourful palette of sounds. The mouthpiece is usually made of ebonite (hard rubber) but may also be made from glass, plastic or metal, though the latter is rare. The ligature binds the reed to the mouthpiece and comes in a variety of shapes and materials, usually thin metal with either one or two screws. Most German system players wind string around the mouthpiece and reed instead of a ligature.
The reed, made from a piece of tall cane, in conjunction with the mouthpiece, acts as a valve (an opening and closing mechanism) through which air passes, creating vibrations in the air column inside the clarinet, generating sound. Reeds come in varying degrees of hardness with lower-numbered reeds being softer. The player will need to test each reed in order to find out the best ones since each are different (always wet the reed just before putting the reed on the mouthpiece). Try to match the shape of the tip of the reed to the tip of the mouthpiece by using a fine file. This hardens it and makes it sound better. Also try to have the back of the reed as flat as possible by running it along a file or a piece of india stone and by pressing it down on a flat surface, like a mirror, just before playing. This reduces or eliminates unwanted hiss from the reed.