All sound comes from vibrations. A vibration is a movement that starts when something is disturbed; the faster something vibrates, the higher the pitch. Pitch is how high or low a sound is; a string on its own makes little sound. It is thin and slips easily through the air. An electric guitar makes little sound unless it is plugged into an amplifier.

A string instrument is made of wood. Its strings vibrate to make the sound; the hollow body pushes the air and makes the sound louder. The body of the instrument pushes the air; a harp's strings are played by plucking them with the fingers. A violin is played with a bow made of a stick and a ribbon of horsehair.

Most woodwinds have a reed. A reed is a small piece of cane or wood. It shakes when air goes across it. A clarinet has a single reed. The reed is made from the cane of a type of grass. Air makes the reed shake, and that makes the sound. A flute has no reed. Its sound comes from air that hits an edge.

A flute or oboe player opens and closes finger holes to change the note. That changes the length of the column of air. In a wind instrument, a longer tube makes a lower note. A tuba needs one so long that it is curled into loops. A piccolo is a small flute that plays very high notes.

Brass players make sound by buzzing their lips into a metal mouthpiece. Percussion instruments, such as drums, make sound when they are hit, shaken or scraped; a piano makes sound when felt hammers strike its metal strings. So a piano is counted with the percussion family. An orchestra has four groups of instruments: strings, woodwinds, brass and percussion.

Flutes made from bone and ivory are among the oldest known instruments. They were found in caves in Germany and are about 40,000 years old. In Jiahu, China, scientists found bone flutes between 7,000 and 9,000 years old. They were made from the wing bones of big birds. They have five to eight finger holes. The best-preserved one has been played.

Words to know

• vibrations: fast shakes
• pitch: how high
• reed: thin cane
• percussion: hit instruments
• flute: wind instrument

The short version

Every instrument makes sound by vibrating. Strings shake when they are plucked or bowed, air shakes inside a flute, and drums shake when they are hit. Instruments sort into four groups: strings, woodwinds, brass and percussion. Some very old flutes were made from bone.

Quick facts

• All sound comes from vibrations, and the faster something vibrates, the higher the pitch.
• A string on its own makes little sound; the hollow body of the instrument pushes the air.
• A flute has no reed: its sound comes from air blown against an edge.
• Flutes made from bone and ivory, found in caves in Germany, are about 40,000 years old.
• Listening for a long time to sounds at or above 85 decibels can damage hearing.