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About A♯8
A♯8 / B♭8 has a frequency of 7.459 kHz in standard tuning, where A4 is fixed at 440 Hz. It is MIDI note 118, outside the range of a standard piano.
In equal temperament every semitone multiplies the frequency by the twelfth root of two (≈1.05946), so A♯8 is 49 semitones above A4: f = 440 × 2^((118 − 69) / 12) = 7,458.62 Hz. The number in the name is the octave in scientific pitch notation, which starts each octave on C.
A♯8 and B♭8 are enharmonic: on a piano or in equal temperament they are the same key and the same frequency, but they are spelled differently depending on the key signature.
A♯8 frequency in different tunings
| Tuning reference | A♯8 frequency |
|---|---|
| A4 = 440 Hz (ISO 16 standard) | 7.459 kHz |
| A4 = 442 Hz (many European orchestras) | 7.493 kHz |
| A4 = 443 Hz (Berlin, Vienna) | 7.509 kHz |
| A4 = 435 Hz (French diapason normal, 1859) | 7.374 kHz |
| A4 = 432 Hz (alternative tuning) | 7.323 kHz |
| A4 = 415 Hz (Baroque pitch) | 7.035 kHz |
| C4 = 256 Hz (scientific pitch) | 7.298 kHz |
Intervals from A♯8
| Interval | Note | Frequency | Ratio (just) |
|---|---|---|---|
| Minor second | B8 | 7.902 kHz | 16:15 |
| Major second | C9 | 8.372 kHz | 9:8 |
| Minor third | C♯9 | 8.87 kHz | 6:5 |
| Major third | D9 | 9.397 kHz | 5:4 |
| Perfect fourth | D♯9 | 9.956 kHz | 4:3 |
| Tritone | E9 | 10.548 kHz | 45:32 |
| Perfect fifth | F9 | 11.175 kHz | 3:2 |
| Minor sixth | F♯9 | 11.84 kHz | 8:5 |
| Major sixth | G9 | 12.544 kHz | 5:3 |
| Minor seventh | G♯9 | 13.29 kHz | 9:5 |
| Major seventh | A9 | 14.08 kHz | 15:8 |
| Octave | A♯9 | 14.917 kHz | 2:1 |
Frequently asked questions
What is the frequency of A♯8?
A♯8 is 7.459 kHz when A4 = 440 Hz (7.323 kHz if A4 = 432 Hz).
What MIDI number is A♯8?
A♯8 is MIDI note number 118.
Is A♯8 on a piano?
No – a standard 88-key piano runs from A0 to C8, so A♯8 is outside its range.