a (musical note)

{{Short description|Musical note}}

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{{stack|{ \new Staff \with{ \magnifyStaff #3/2 } << \time 2/1 \override Score.TimeSignature #'stencil = ##f { \clef bass a1_A \clef treble a'_A } >> }}}

A is a musical note equivalent to 440 Hz in typical A440 tuning. It is the sixth note of La and the tenth semitone of the fixed-do solfège.

Its enharmonic equivalents are B{{music|double flat}} (B double-flat) and G{{music|double sharp}} (G double-sharp).

"A" is generally used as a standard for tuning. When the orchestra tunes, the oboe plays an "A" and the rest of the instruments tune to match that pitch. Every string instrument in the orchestra has an A string, from which each player can tune the rest of their instrument.

"A" is also used in combination with a number (e.g. A-440) to label the pitch standard. The number designates the frequency in hertz. A lower number indicates a lower pitch.

The International Standards Organization (ISO) has standardized the pitch at A-440.{{cite web|url=https://www.iso.org/standard/3601.html|title=ISO 16:1975 Acoustics – Standard Tuning Frequency|publisher=International Standards Organization|access-date=10 December 2019}} However, tuning has varied over time, geographical region, or instrument maker. In 17th-century Europe, tunings ranged from about A-374 to A-403, approximately two to three semitones below A-440. Historical examples exist of instruments, tuning forks, or standards ranging from A-309 to A-455.3,{{cite web|last=Suits|first=B. H.|title=Physics of Music Notes – Scales: Just vs Equal Temperament|url=https://pages.mtu.edu/~suits/scales.html|publisher=Michigan Technological University|date=1998|access-date=5 February 2024}} a difference of almost six semitones. Although the official standard today is A-440, some orchestral groups and chamber groups prefer to tune a little higher, at A-442 or even A-444. Baroque pitch is usually cited as A-415, which is a semitone lower than modern pitch.

A₀ is the lowest note on standard pianos with 88 keys, and the rarer older 85-key pianos.