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Iso 16

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Title: Iso 16  
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Subject: List of International Organization for Standardization standards
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Iso 16

For other uses, see A440.

A440, which has a frequency of 440 Hz, is the musical note A above middle C and serves as a general tuning standard for musical pitch.

Prior to the standardization on 440 Hz, many countries and organizations followed the Austrian government's 1885 recommendation of 435 Hz. 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.[1] This standard was taken up by the International Organization for Standardization in 1955 (reaffirmed by them in 1975) as ISO 16.[2] Although not universally accepted, since then it has served as the audio frequency reference for the calibration of acoustic equipment and the tuning of pianos, violins, and other musical instruments.

A440 is widely used as concert pitch in United Kingdom[3] and the United States. In continental Europe the frequency of the A is commonly 442 Hz and 443 Hz.[4][5] In the period instrument movement, a consensus has arisen around a modern baroque pitch of 415 Hz (currently, A flat), baroque for some special church music (Chorton pitch) at 466 Hz (A sharp) and classical pitch at 432 Hz.[6]

The A above middle C is sometimes referred to as Concert A. (The C above Concert A is called Concert C.)

File:Sine wave 440.ogg
5 seconds of sine wave at 440 Hz

Problems playing this file? See media help.

A440 is often used as a tuning reference in just intonation regardless of 1/1 or key. For example, A is common to all stringed instruments.

See also


External links

  • ISO 16:1975 as described in their catalog
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