A tuba is a brass instrument that has four parts. One part is the mouthpiece, which is where the musician blows air into the instrument. Another is the tube, which is considerably long in order to give the instrument its low pitch. The bell of the tuba is where the sound comes out of the instrument, and the valves, or the valve assembly, allows the musician to create different notes.
The mouthpiece is one of the tuba parts. In order to make a sound on a tuba, the player must form a seal with his or her lips against the mouthpiece and blow air into the instrument while vibrating the lips. The instrument will not sound without vibration. The mouthpiece is usually located near the bell of the tuba, though it is attached to the small end of the tube.
By far the largest of the tuba parts is the tube. This part of the instrument ranges in length from 12 to 18 feet (3.7 to 5.5 meters), with shorter tubas tuned to higher keys than longer tubas are. Though tubas come in a variety of different shapes, the tube is always coiled around in some way so that a single musician is able to comfortably hold and play the instrument. Concert tubas are often coiled in an oblong shape, while marching tubas may be coiled into a circle that is designed to fit around the musician's shoulders.
Attached to the tube at the end opposite the mouthpiece is another of the tuba parts. The bell is conical in shape, which allows the sound to be dispersed from the instrument. Tuba bells may point directly upward, as in the case of a classical concert tuba or toward the front, as the bell of the recording tuba does.
Valves are the tuba parts responsible for changing the pitch of the instrument so that various notes can be played. Tubas designed for beginners usually have three valves, while those for professionals have between four and six. More valves are useful in professional instruments because the three-valved tuba tends to go sharp when all three valves are depressed. There are two main types of valves: piston valves, which require regular oiling in order to slide freely in their chambers, and rotary valves which are more complex in design require less routine maintenance. The valve type does not affect the sound of the instrument.