A♯ (musical note)


A , or la dièse, is the eleventh semitone of the solfege. In some countries 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.
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 for a discussion of historical variations in frequency.

Designation by octave

Scales

Common scales beginning on A