A (A-flat; also called la bémol) is the ninth

semitone A semitone, also called a 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 two adjacent no ...

of the

solfège In music, solfège (, ) or solfeggio (; ), also called sol-fa, solfa, solfeo, among many names, is a music education method used to teach aural skills, Pitch (music), pitch and sight-reading of Western classical music, Western music. Solfège is ...

. It lies a

diatonic semitone A semitone, also called a 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 two adjacent no ...

above G and a

chromatic semitone In modern Western tonal music theory an augmented unison or augmented prime is the interval between two notes on the same staff position, or denoted by the same note letter, whose alterations cause them, in ordinary equal temperament, to be one ...

below A, thus being

enharmonic In modern musical notation and tuning, an enharmonic equivalent is a note, interval, or key signature that is equivalent to some other note, interval, or key signature but "spelled", or named differently. The enharmonic spelling of a written n ...

to G, even though in some

musical tuning In music, there are two common meanings for tuning: * Tuning practice, the act of tuning an instrument or voice. * Tuning systems, the various systems of pitches used to tune an instrument, and their theoretical bases. Tuning practice Tun ...

s, A will have a different sounding pitch than G. When calculated in

equal temperament An equal temperament is a musical temperament or tuning system, which approximates just intervals by dividing an octave (or other interval) into equal steps. This means the ratio of the frequencies of any adjacent pair of notes is the same, wh ...

with a reference of A above middle C as 440 Hz, the

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of the A above middle C (or A₄) is approximately 415.305 Hz. See

pitch (music) Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale, or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" in the sense associated with musical melodie ...

for a discussion of historical variations in frequency. The notes A and G are the only notes to have only one enharmonic, since they cannot be reached in any other way by a single or double sharp or a single or double flat from any of the seven white notes.

Designation by octave

Scales

Common scales beginning on A

A major A major (or the key of A) 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 key of A major is the only k ...

: A B C D E F G A * A natural minor: A B C D E F G A * A

harmonic minor In music theory, the minor scale is three scale patterns – the natural minor scale (or Aeolian mode), the harmonic minor scale, and the melodic minor scale (ascending or descending) – rather than just two as with the major scale, which also ...

: A B C D E F G A * A

melodic minor In music theory, the minor scale is three scale patterns – the natural minor scale (or Aeolian mode), the harmonic minor scale, and the melodic minor scale (ascending or descending) – rather than just two as with the major scale, which al ...

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 any heptatonic 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 either two or three whole steps, ...
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 Mixolydian mode may refer to one of three things: the name applied to one of the ancient Greek ''harmoniai'' or ''tonoi'', based on a particular octave species or scale; one of the medieval church modes; or a modern musical mode or diatonic scal ...

: 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 In music, the acoustic scale, overtone scale, Lydian dominant scale, Lydian 7 scale, or the Pontikonisian Scale is a Heptatonic scale, seven-note synthetic scale, synthetic Scale (music), scale. : This differs from the major scale in having an ...

: 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

Designation by octave

Scales

Common scales beginning on A

Diatonic scale In music theory, a diatonic scale is any heptatonic 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 either two or three whole steps, ...s

Jazz melodic minor

See also

Diatonic scale In music theory, a diatonic scale is any heptatonic 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 either two or three whole steps, ...
s