Musical notes produced by musical instruments or singers are formed by a set of different frequencies, with a basic or fundamental frequency, which is characteristic of the note. An “A”, for example, will have a basic frequency of 440 Hz. Each different frequency combination results in a pressure waveform, determined by factors such as the material the instrument is made of, the shape of the sounding board, and the force used to produce the sound.
An “A” of a violin is different from the “A” of a flute or a singer. Although all these notes have the same dominant frequency, the shape of the pressure wave is different. A flute produces a sound with an almost pure sine wave, whereas the sound produced by a violin is a more complex wave.
Timbre is associated with the shape of the wave and allows us to distinguish sounds of the same frequency, produced by different instruments. The timbre is characterized by the composition of frequencies that constitute the sound wave emitted by the instrument. Timbre is also called sound quality .
Some instruments, given their peculiar construction, have an unparalleled quality or timbre. We can analyze the sound wave with suitable equipment and check which frequencies are important. Any sound wave can be described as a superposition of waves of a single frequency.
The combination of frequencies characterizes the sound and also determines whether a sound is pleasant or not. The pleasant sound sensation occurs when the frequencies that make up the sound are multiples of each other, that is, we have a basic frequency and the others are two, three or four times greater, we call them harmonics .
In contrast, an unpleasant sound has a composition of frequencies that are unrelated to each other. These waves do not have a defined period.