 The brass instruments are in fact wind instruments made of brass. They consist of a mouth piece, a cylindrical section of hollow tube and a flared opening. The long section of the tube is usually coiled and has no holes. The player blows into a mouthpiece at one end of the tube, setting the air column vibrating throughout the tube. The saxophone is built like a brass instrument, but it uses a reed to produce the vibration of the air column. In a brass instrument, the force of the lips varies to make the vibrating column divide into two halves, three thirds, and so on. This gives an ascending series of notes called harmonics. Opening extra lengths of tubing then produces other notes that are not in this harmonic series. The pitch of the note depends on the length of the tube, a shorter tube giving a higher note, and a longer one a lower note. Blowing harder makes the sound louder.
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LOW PRESSURE With low lip pressure, the air column vibrates in two halves and each half gives the note middle C. The length of the tube is therefore twice as long as a woodwind instrument sounding the same note. |
INCREASED PRESSURE Raising the lip pressure makes the air column vibrate in three thirds. Each vibrating section is two-thirds the length of the previous section, raising the pitch of the note to G. |
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INCREASED LENGTH To play an E, which is not in the harmonic series, the player keeps the air vibrating in three thirds and increases the total length of the tube. This extends the vibrating air column to four-fifths of the total length of the tube, giving an E. Each vibrating section becomes four-fifths the length for middle C. This is achieved in a fixed length instrument like the flute and recorder by keeping the first five of the seven holes covered. This extends the vibrating air column to four-fifths of the total length of the tube, giving an E. |
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THE TROMBONE The trombone has a section of tubing called a slide that can be moved in and out. The player pushes out the slide to lengthen the vibrating air column and produce notes that are not in the harmonic series. |
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THE TRUMPETThe trumpet has three pistons that are pushed down to open up extra sections of tubing and play notes that are not in the harmonic series. Up to six different notes can obtained by using different combinations of the three pistons. |
HOW PISTONS AND VALVES WORK On instruments such as the trumpet and tuba, each valve has a loop of tubing attached to it. Normally, the spring pushes against the piston, keeping the valve closed and shutting off access to the loop. But when the piston is depressed, the valve is opened and the air column is diverted through the loop to effectively lengthen the vibrating air column. |
