A440 (also known asStuttgart pitch[1]) is themusical pitch corresponding to an audio frequency of 440Hz, which serves as a tuning standard for themusical note ofA abovemiddle C, orA4 inscientific pitch notation. It is standardized by theInternational Organization for Standardization asISO 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 tunepianos,violins, and othermusical instruments.
Before standardization to 440 Hz, many countries and organizations followed the French standard since the 1860s of 435 Hz, which had also been theAustrian government's 1885 recommendation.[2]Johann Heinrich Scheibler recommended A440 as a standard in 1834 after inventing the "tonometer" to measurepitch,[3] and it was approved by theSociety of German Natural Scientists and Physicians at a meeting inStuttgart the same year.[4]
The American music industry reached an informal standard of 440 Hz in 1926, and some began using it in instrument manufacturing.[citation needed]
In 1936, theAmerican Standards Association recommended that the A above middle C be tuned to 440 Hz.[5]
In 1937 SirJames Swinburne, an electrical engineer and avid amateur musician, delivered a lecture to theRoyal Musical Association on "The Ideal Scale," discussing the possibility of tuning a scale to pure ratios and adjusting these ratios to maintain consonance across different keys. The following year, Swinburne represented the Musical Association at a preliminary conference to determine the British stance on concert pitch. British piano tuners had adopted A439 as the standard in 1899, but Swinburne pointed out that 439 was a prime number, whereas 440 could be more easily factored and electronically synthesized. In May of 1939, delegates from France, Germany, The Netherlands, Italy, and England convened at Broadcasting House in London, the headquarters of the BBC, to address the issue of concert pitch. Representatives from Switzerland and the United States participated via mail. The other European delegates concurred with Swinburne's position and agreed to a standard of A440.
This standard was taken up by theInternational Organization for Standardization in 1955 as Recommendation R 16,[6] before being formalised in 1975 asISO 16.[7]
The A440 standard is not universally adhered to. Early-music ensembles continue to use older, lower pitch levels.Leonard Bernstein often tuned the New York Philharmonic to A442, leading to complaints from the piano tuners’ union, although he claimed both the New York and Boston orchestras had used this higher pitch for years.
A440 is widely used asconcert pitch in theUnited Kingdom[8] and theUnited States.[9] In continental Europe the frequency of A4 commonly varies between 440 Hz and 444 Hz.[8]In theperiod instrument movement, a consensus has arisen around a modernbaroque 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 period cantatas ofBach)[10] known asChorton pitch at 466 Hz (with 440 Hz corresponding to A♭), andclassical pitch at 427–430 Hz.[10]
A440 is often used as a tuning reference injust intonation regardless of the fundamental note orkey.
The US time and frequency stationWWV broadcasts a 440 Hz signal at two minutes past every hour, withWWVH broadcasting the same tone at the first minute past every hour. This was added in 1936 to aid orchestras in tuning their instruments.[11]
| Preceded by ISO 15 | Lists of ISOs ISO 16 | Succeeded by ISO 17 |
