A♯ (musical note)

A♯ (A-sharp), or la dièse, is the eleventh semitone of the solfege. In some countries (where B is known as H) it is informally called B.

This note lies a chromatic semitone above A and a diatonic semitone below B, thus being enharmonic to si bémol or B♭ (B-flat).

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of the A♯ above middle C is approximately 466.164 Hz. See pitch (music) for a discussion of historical variations in frequency.

Designation by octave

Scientific designation	Helmholtz designation	Octave name	Frequency (Hz)
A♯₋₁	A♯͵͵͵ or ͵͵͵A♯ or AAAA♯	Subsubcontra	14.568
A♯₀	A♯͵͵ or ͵͵A♯ or AAA♯	Subcontra	29.135
A♯₁	A♯͵ or ͵A♯ or AA♯	Contra	58.270
A♯₂	A♯	Great	116.541
A♯₃	a♯	Small	233.082
A♯₄	a♯′	One-lined	466.164
A♯₅	a♯′′	Two-lined	932.328
A♯₆	a♯′′′	Three-lined	1864.655
A♯₇	a♯′′′′	Four-lined	3729.310
A♯₈	a♯′′′′′	Five-lined	7458.620
A♯₉	a♯′′′′′′	Six-lined	14917.240
A♯₁₀	a♯′′′′′′′	Seven-lined	29834.481