A♯4 on the staff and the piano
On the treble clef, A♯4 sits in the second space from the bottom. The sharp sign raises A4 by one semitone. The same key can also be written B♭4, with a flat on the next line or space up.
On the piano, A♯4 is key 50 of 88, octave 4 - the black key between A4 and B4. It is 10 semitones above middle C (C4, key 40).
Play it on the online piano, or see all 88 note frequencies on one page.
A♯4 at a glance
All values assume twelve-tone equal temperament at the international standard pitch of A4 = 440 Hz. In that system every semitone has the same size - a frequency ratio of 2^(1/12) - so A♯4 is exactly 440 × 2^(1/12) Hz. Under alternative references the note shifts with the reference: at A4 = 432 Hz, A♯4 becomes 457.69 Hz.
A♯ in every octave
| Note | Frequency | MIDI | Piano key |
|---|---|---|---|
| A♯0 | 29.14 Hz | 22 | 2 |
| A♯1 | 58.27 Hz | 34 | 14 |
| A♯2 | 116.54 Hz | 46 | 26 |
| A♯3 | 233.08 Hz | 58 | 38 |
| A♯4 ← | 466.16 Hz | 70 | 50 |
| A♯5 | 932.33 Hz | 82 | 62 |
| A♯6 | 1864.7 Hz | 94 | 74 |
| A♯7 | 3729.3 Hz | 106 | 86 |
Each octave doubles the frequency - the simplest relationship in music, and the reason notes an octave apart sound like “the same note, higher”.
Who plays A♯4
A♯4 is within the usual range of the piano, guitar, violin, viola, cello, flute, clarinet, trumpet and trombone. Among voice types it falls in the usual range of soprano, mezzo-soprano, alto and tenor.
- Piano: A0–C8
- Guitar (standard tuning): E2–E6
- Violin: G3–A7
- Viola: C3–E6
- Cello: C2–A5
- Flute: C4–C7
- Clarinet (B♭): D3–B♭6
- Trumpet (B♭): E3–B♭5
- Trombone (tenor): E2–F5
- Soprano: C4–C6
- Mezzo-soprano: A3–A5
- Alto (contralto): F3–F5
- Tenor: C3–C5
Ranges are approximate: they are the commonly cited sounding (concert) pitches, and real ranges vary by player, instrument, tuning and repertoire. Guitar, bass guitar and double bass are written an octave higher than they sound; B♭ clarinet and trumpet are written a whole tone higher.
Neighboring notes
One semitone down is A4 at 440.00 Hz; one semitone up is B4 at 493.88 Hz. Need a frequency between notes, or a different waveform? The tone generator plays anything from 20 Hz to 20 kHz; the note ↔ frequency converter does the math both directions, and the chromatic tuner listens to your instrument and shows the offset in cents.