Musical sounds have wave patterns that are evenly spaced and regular, while noises—unpleasant sounds—usually have irregular patterns. Each musical note has a specific pitch that is the same for every instrument. The lowest pitch for each note is called the fundamental frequency (or, simply, fundamental). The note A, for example, is produced by 440 vibrations per second (440 Hz). No musical instrument produces a perfectly pure note. Each is coloured by the presence of other, fainter notes of higher pitch, called overtones. These are different for each musical instrument, and so give that instrument its characteristic sound, or timbre.

Musical instruments

Musical notes may be produced by bowing or plucking a string (string instruments, such as violin or cello), blowing into a pipe (wind instruments, such as the clarinet and brass instruments such as the trumpet) or striking something (percussion instruments, such as the drums or triangle).

​​​​​​​In string instruments, the vibration of the string sets the air inside a soundbox vibrating. The vibration of the soundbox is called resonance: it makes the sound produced louder and richer in quality. The pitch is varied by both the tightness of the string and by varying its length (which the player achieves by pressing down the string on the fingerboard with their finger).

Trumpet players produce sounds from their instruments by vibrating their lips. This causes the air inside to vibrate as well. They can play different notes (of higher or lower pitch) both by changing the tension of their lips and by opening or closing valves in the tube, which alters the length of the air column.