A (A-sharp; French: ) is the eleventh

semitone A semitone, also called a minor second, half step, or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically. It is defined as the interval between ...

of the

solfège In music, solfège (British English or American English , ) or solfeggio (; ), also called sol-fa, solfa, solfeo, among many names, is a mnemonic used in teaching aural skills, Pitch (music), pitch and sight-reading of Western classical music, W ...

. This note lies a chromatic semitone above A and a

diatonic semitone A semitone, also called a minor second, half step, or a half tone, is the smallest interval (music), musical interval commonly used in Western tonal music, and it is considered the most Consonance and dissonance#Dissonance, dissonant when sounde ...

below B, thus being

enharmonic In music, two written notes have enharmonic equivalence if they produce the same pitch but are notated differently. Similarly, written intervals, chords, or key signatures are considered enharmonic if they represent identical pitches that ar ...

to B (French: ). When calculated in

equal temperament An equal temperament is a musical temperament or Musical tuning#Tuning systems, tuning system that approximates Just intonation, just intervals by dividing an octave (or other interval) into steps such that the ratio of the frequency, frequencie ...

with a reference of A above

middle C C or Do is the first note of the C major scale, the third note of the A minor scale (the relative minor of C major), and the fourth note (G, A, B, C) of the Guidonian hand, commonly pitched around 261.63 Hz. The actual frequency has d ...

as 440 Hz, the

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

of the A above middle C is approximately 466.164Hz. See

pitch (music) Pitch is a perception, perceptual property that allows sounds to be ordered on a frequency-related scale (music), scale, or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" in the sense associate ...

for a discussion of historical variations in frequency.

Designation by octave

Scales

Common scales beginning on A

A major A major is a major scale based on A, with the pitches A, B, C, D, E, F, and G. Its key signature has three sharps. Its relative minor is F-sharp minor and its parallel minor is A minor. The A major scale is: Changes needed for the ...

: A B C D E F G A * A natural minor: A B C D E F G A * A harmonic minor: A B C D E F G A * A melodic minor ascending: A B C D E F G A * A melodic minor descending: A G F E D C B A

Diatonic scale In music theory a diatonic scale is a heptatonic scale, heptatonic (seven-note) scale that includes five whole steps (whole tones) and two half steps (semitones) in each octave, in which the two half steps are separated from each other by eith ...
s

* A Ionian: A B C D E F G A * A Dorian: A B C D E F G A * A Phrygian: A B C D E F G A * A Lydian: A B C D E F G A * A Mixolydian: A B C D E F G A * A Aeolian: A B C D E F G A * A Locrian: A B C D E F G A

Jazz melodic minor

* A ascending melodic minor: A B C D E F G A * A Dorian ♭2: A B C D E F G A * A Lydian augmented: A B C D E F G A * A Lydian dominant: A B C D E F G A * A Mixolydian ♭6: A B C D E F G A * A Locrian ♮2: A B C D E F G A * A altered: A B C D E F G A

References