A (A-flat; also called la bémol) is the ninth semitone of the solfège.
It lies a diatonic semitone above G and 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 A4) is approximately 415.305 Hz.[1] See pitch (music) 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.
| Scientific designation | Helmholtz designation | Octave name | Frequency (Hz) | |
|---|---|---|---|---|
| A−1 | A͵͵͵ or ͵͵͵A or AAAA | Octocontra | ||
| A0 | A͵͵ or ͵͵A or AAA | Subcontra | ||
| A1 | A͵ or ͵A or AA | Contra | ||
| A2 | A | Great | ||
| A3 | a | Small | ||
| A4 | a | One-lined | ||
| A5 | a | Two-lined | ||
| A6 | a | Three-lined | ||
| A7 | a | Four-lined | ||
| A8 | a | Five-lined | ||
| A9 | a | Six-lined | ||
| A10 | a | Seven-lined |