How do musical instruments make the sounds you hear? In one way or another, it all comes down to vibrations; we hear sounds when the particles of air around us move back and forth very fast in tiny movements. You can’t see these movements happening, but we hear them as sound! To make music, we use instruments or our voices to set these vibrations in motion.
There are many different musical instruments, so it helps to think of them as members of “families” that make sounds in similar ways. Let’s explore the most common instrument families found in classical music.
Instruments in the string family—such as violins, cellos, and even guitars—make noise with the help of strings pulled very tightly. The musician causes the strings to vibrate in a variety of ways, depending on the instrument and style of music. For example, a violinist often moves a bow made of horsehair (yes, from the tails of horses!) across the strings to create the sound, or sometimes plucks the strings with their fingers.
Most string instruments have their strings suspended over hollow wooden bodies that make the sound louder. Different notes are made by pressing down the strings in different places, making the vibrating part of the string shorter or longer.
In chamber music, the most common string instruments are violins, violas, cellos, and double basses.
Not all instruments have strings. Some make sound when air is blown through a tube! In the family called woodwinds, most of the instruments are made of wood, and the vibration is created when the musician blows air through or across a very thin piece of wood called a reed. The musician uses their fingers to cover holes along the tube (sometimes with the help of metal keys that cover the holes). Covering different combinations of holes produces different notes, as this changes how the air inside the tube vibrates. Some examples of instruments of this type are the clarinet, oboe, and bassoon.
Other instruments in this family, such as the flute, are a little different. Instead of using a reed, the musician creates the vibration by blowing across an opening at one end of the tube. (You can try something similar by blowing across the top of a plastic or glass bottle.) A flute has keys to cover different holes along the tube, just like the other woodwind instruments.
There is another family of instruments that make sound by means of musicians blowing air into them: the brass! For brass instruments, the vibration is created when the musicians buzz their lips while blowing air into one end. All of these instruments are made of metal. In the case of a trumpet, French horn, or tuba, the musician changes the amount of air that vibrates inside using valves that open up different sized sections of tubing. Another instrument in this family is the trombone, which uses a movable slide to change the overall length of the tube.
There is one last family of instruments we haven’t discussed: percussion. There are many, many, types of percussion instruments, and each makes a different sound. Examples include drums, xylophones, cymbals, and even triangles! To make noise, a percussion instrument is struck by sticks, hammers, mallets, a musician’s hands, or sometimes other objects. (Our word “percussion” comes from an old Latin word that means “to strike.”)
In the case of a drum, the vibration is created when the musician hits or taps the tightly stretched skin that covers a round, hollow body. With other percussion instruments, such as a triangle or cymbal, the entire instrument vibrates when struck.
Believe it or not, the piano is often considered a percussion instrument (even though it contains many strings) because the sound is made when small hammers hit the taut strings!