Brass instruments get their sound from the vibrations of the musician's lips. This works by the player putting their lips tightly into the mouthpiece and blowing. The vibration between the lips and mouthpiece causes the air to vibrate down the long brass tube.
Musicians can vary the notes they play, the tone of the music, and the loudness by controlling the vibration of their lips. This takes a lot of practice to get right.
Valves and Slides
Brass instruments that are a fixed length can only make a few notes. This is the way all horns were for a long time. Then the slide and the valve were introduced. These allow the musician to change the length of the tube. They are each different in how they work.
Valves
When you look at all those tubes and curves in a trumpet, French horn, or tuba it can look almost like a mess of spaghetti. However, all those tubes help the instrument to make different sounds and notes. The buttons on these instruments are called valves. By pressing the valves the player adds in additional length to the tube.
Valves on a Trumpet
The air that is blown into the mouthpiece eventually goes to the end, or bell, of the brass instrument. But it doesn't always travel through all those tubes you see. When a valve is pressed an additional curve or length of tubing is added into the path that the air takes. The musician can add in and take out sections of the tube in order to make a wide variety of notes.
Slide
Another way to change the length of the tube is by using a slide. The slide is used in the trombone. By moving a long section of the tube in and out, the musician can change the length of the tube and, therefore, the notes. Since the tube can slide gradually, the musician can "slide" between notes giving a smooth sound.
Bore and Bell
The tube of the instrument is called the bore. The end, where it flares out wide, is called the bell. The shape, width, and length of the bore and bell have a lot to do with the tone of the brass instrument. They can cause the instrument to have a crisp blaring tone like the trumpet or a warm mellow tone like the French horn.
Bells on brass instruments
Fun Facts about How Brass Instruments Work
The slide was invented in the 15th century, hundreds of years before the valve.
The slide can smoothly move from one note to the next, but can't change notes as fast as the valve.
The French horn really does come from France. If you stretched out a French horn it would be around 18 feet long!
The tone of the French horn is changed by putting your right hand into the bell of the horn. Musicians actually change the sound of the horn by how they place their hand into the bell.
Trombones play notes in the lower pitch range similar to a cello or a bassoon.
The tuba takes a lot of breath and strong lips (and arms!) to play.
