A (A-sharp; also called la dièse) is the eleventh

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 solfege. In some countries (where B is known as H) it is informally called B. This note lies 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 ...

above A and a

diatonic semitone A semitone, also called a 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 sounded harmonically ...

below B, thus being enharmonic to ''si bémol'' or B (B-

flat Flat or flats may refer to: Architecture * Flat (housing), an apartment in the United Kingdom, Ireland, Australia and other Commonwealth countries Arts and entertainment * Flat (music), a symbol () which denotes a lower pitch * Flat (soldier), ...

). When calculated in equal temperament 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 is approximately 466.164 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 melodi ...

for a discussion of historical variations in

Designation by octave

Scales

Common scales beginning on A

* A major: 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 scales

* 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: 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