pitch

In music, the technical term used to describe how high or low a note is. It depends on the frequency (number of vibrations per second) of the sound, which is measured in hertz (Hz). Pitch also refers to the standard to which instruments are tuned. Nowadays the internationally agreed-upon pitch is the A above middle C (A4 or a'), which has a frequency of 440 Hz (vibrations per second). This is often known as concert pitch.

Pitch can now be measured accurately by electronic tuning devices. These are beginning to replace the traditional tuning fork, but it is still normal practice for orchestras to tune to an oboe playing A4.

Absolute pitch (also called perfect pitch) is the ability to name any note heard, or to sing any note asked for. It is now considered to be learned at a very young age through exposure to a well-tuned instrument. A person who has perfect pitch does not necessarily have any other musical ability. Perfect pitch is not particularly rare and many musicians have it.

For any musical note, the pitch is determined by what the ear perceives as its fundamental frequency. In stringed instruments this depends on the length, tension, and composition of the vibrating string, and in wind instruments on the length of the tube. Some instruments, mainly in the percussion family, are of indefinite pitch and are referred to as ‘untuned’ instruments. In organ terminology, ranks of pipes are classified in wavelength pitch, such as 4-foot, 8-foot, or 16-foot, according to the octave range in which they fall.

The internationally-recognized standard pitch of 440 Hz at A above middle C was set in 1955 by the International Organization for Standardization, and ended centuries of confusion, although in the 1990s some orchestras and ensembles used 441 Hz and 442 Hz to give a bright sound in contrast to the normal 440 Hz. Before 1955 pitch had varied at different times and from country to country, from 410 Hz to 480 Hz. The general trend had been for a gradual rise in standard pitch, often encouraged by wind-instrument makers anxious to achieve a more brilliant sound. This meant that music in the newer pitch sometimes became too high for singers, and also required many of the stringed instruments designed for the old, lower pitch to be modified. Nearly all the great stringed instruments made by Antonio Stradivari, Joseph Guarneri, and the Amati family were converted to accommodate the new pitch. At times two pitches were in use, the higher for orchestral performances and the lower ‘classical’ or ‘French’ pitch for church and purely vocal music. This French pitch, known also as ‘diapason normal’, had A4 or a' at 435 Hz and was fixed in Paris in 1849.