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A440 (also known as Stuttgart pitch) is the musical pitch corresponding to an audio frequency of 440 Hz, which serves as a tuning standard for the
A440 is widely used as
musical note
In music, a note is the representation of a musical sound.
Notes can represent the pitch and duration of a sound in musical notation. A note can also represent a pitch class.
Notes are the building blocks of much written music: discretizatio ...
of A above middle C, or A4 in scientific pitch notation
Scientific pitch notation (SPN), also known as American standard pitch notation (ASPN) and international pitch notation (IPN), is a method of specifying musical pitch by combining a musical note name (with accidental if needed) and a number ide ...
. It is standardized by the International Organization for Standardization
The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Art ...
as ISO 16. While other frequencies have been (and occasionally still are) used to tune the first A above middle C, A440 is now commonly used as a reference frequency to calibrate acoustic equipment and to tune pianos
The piano is a stringed keyboard instrument in which the strings are struck by wooden hammers that are coated with a softer material (modern hammers are covered with dense wool felt; some early pianos used leather). It is played using a keyboa ...
, violins, and other musical instruments
A musical instrument is a device created or adapted to make musical sounds. In principle, any object that produces sound can be considered a musical instrument—it is through purpose that the object becomes a musical instrument. A person who pl ...
.
History and use
Before standardization on 440 Hz, many countries and organizations followed the French standard since the 1860s of 435 Hz, which had also been theAustria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
n government's 1885 recommendation. Johann Heinrich Scheibler recommended A440 as a standard in 1834 after inventing the "tonometer" to measure pitch, and it was approved by the Society of German Natural Scientists and Physicians at a meeting in Stuttgart the same year.
The American music industry reached an informal standard of 440 Hz in 1926, and some began using it in instrument manufacturing.
In 1936, the American Standards Association recommended that the A above middle C be tuned to 440 Hz. This standard was taken up by the International Organization for Standardization
The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Art ...
in 1955 as Recommendation R 16, before being formalised in 1975 as ISO 16.
It is designated A4 in scientific pitch notation because it occurs in the octave that starts with the fourth C key on a standard 88-key piano
The piano is a stringed keyboard instrument in which the strings are struck by wooden hammers that are coated with a softer material (modern hammers are covered with dense wool felt; some early pianos used leather). It is played using a keybo ...
keyboard. On MIDI
MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and ...
, A440 is note 69 (0x45 hexadecimal).
Modern practices
A440 is widely used as concert pitch
Concert pitch is the pitch reference to which a group of musical instruments are tuned for a performance. Concert pitch may vary from ensemble to ensemble, and has varied widely over music history. The most common modern tuning standard uses ...
in the United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
and the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
. In continental Europe the frequency of A4 commonly varies between 440 Hz and 444 Hz.
In the period instrument
In the historically informed performance movement, musicians perform classical music using restored or replicated versions of the instruments for which it was originally written. Often performances by such musicians are said to be "on authentic ...
movement, a consensus has arisen around a modern ''baroque pitch'' of 415 Hz (with 440 Hz corresponding to A), a 'baroque' pitch for some special church music (in particular, some German church music, e.g. the pre-Leipzig
Leipzig ( , ; Upper Saxon: ) is the most populous city in the German state of Saxony. Leipzig's population of 605,407 inhabitants (1.1 million in the larger urban zone) as of 2021 places the city as Germany's eighth most populous, as ...
period cantatas of Bach
Johann Sebastian Bach (28 July 1750) was a German composer and musician of the late Baroque period. He is known for his orchestral music such as the ''Brandenburg Concertos''; instrumental compositions such as the Cello Suites; keyboard wor ...
)Oxford Composer Companion JS Bach, pp. 369–372. Oxford University Press, 1999 known as '' Chorton pitch'' at 466 Hz (with 440 Hz corresponding to A), and ''classical pitch'' at 427–430 Hz.
A440 is often used as a tuning reference in just intonation regardless of the fundamental note or key.
The US time and frequency station WWV broadcasts a 440 Hz signal at two minutes past every hour, with WWVH
WWVH is the callsign of the U.S. National Institute of Standards and Technology's shortwave radio time signal station located at the Barking Sands Missile Range, in Kekaha, on the island of Kauai in the state of Hawaii.
WWVH is the Pacific si ...
broadcasting the same tone at the first minute past every hour. This was added in 1936 to aid orchestras in tuning their instruments.
See also
* History of pitch standards in Western music *Electronic tuner
In music, an electronic tuner is a device that detects and displays the pitch of musical notes played on a musical instrument. "Pitch" is the perceived fundamental frequency of a musical note, which is typically measured in Hertz. Simple tuner ...
References