A♭ (musical note)

A♭ (A-flat; also called la bémol) is the ninth semitone of the solfège.

It lies a diatonic semitone above Gand a chromatic semitone below A, thus being enharmonic to G♯, even though in some musical tunings, A♭ will have a different sounding pitch than G♯.

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of the A♭ above middle C (or A♭₄) is approximately 415.305 Hz. See pitch (music) for a discussion of historical variations in frequency.

A♭/G♯ is the only note to have only one other enharmonic.

Designation by octave

Scientificdesignation	Helmholtzdesignation	Octave name	Frequency (Hz)
A♭₋₁	A♭͵͵͵ or ͵͵͵A♭ or AAAA♭	Octocontra	12.978
A♭₀	A♭͵͵ or ͵͵A♭ or AAA♭	Subcontra	25.957
A♭₁	A♭͵ or ͵A♭ or AA♭	Contra	51.913
A♭₂	A♭	Great	103.826
A♭₃	a♭	Small	207.652
A♭₄	a♭′	One-lined	415.305
A♭₅	a♭′′	Two-lined	830.609
A♭₆	a♭′′′	Three-lined	1661.219
A♭₇	a♭′′′′	Four-lined	3322.438
A♭₈	a♭′′′′′	Five-lined	6644.875
A♭₉	a♭′′′′′′	Six-lined	13289.750
A♭₁₀	a♭′′′′′′′	Seven-lined	26579.501