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About C♯6
C♯6 / D♭6 has a frequency of 1.109 kHz in standard tuning, where A4 is fixed at 440 Hz. It is MIDI note 85 and key number 65 on an 88-key piano.
In equal temperament every semitone multiplies the frequency by the twelfth root of two (≈1.05946), so C♯6 is 16 semitones above A4: f = 440 × 2^((85 − 69) / 12) = 1,108.73 Hz. The number in the name is the octave in scientific pitch notation, which starts each octave on C.
C♯6 and D♭6 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.
C♯6 frequency in different tunings
| Tuning reference | C♯6 frequency |
|---|---|
| A4 = 440 Hz (ISO 16 standard) | 1.109 kHz |
| A4 = 442 Hz (many European orchestras) | 1.114 kHz |
| A4 = 443 Hz (Berlin, Vienna) | 1.116 kHz |
| A4 = 435 Hz (French diapason normal, 1859) | 1.096 kHz |
| A4 = 432 Hz (alternative tuning) | 1.089 kHz |
| A4 = 415 Hz (Baroque pitch) | 1.046 kHz |
| C4 = 256 Hz (scientific pitch) | 1.085 kHz |
Where to play C♯6 on a guitar
Standard tuning (E A D G B E), frets 0–22.
- 1st string (high E), fret 21
Intervals from C♯6
| Interval | Note | Frequency | Ratio (just) |
|---|---|---|---|
| Minor second | D6 | 1.175 kHz | 16:15 |
| Major second | D♯6 | 1.245 kHz | 9:8 |
| Minor third | E6 | 1.319 kHz | 6:5 |
| Major third | F6 | 1.397 kHz | 5:4 |
| Perfect fourth | F♯6 | 1.48 kHz | 4:3 |
| Tritone | G6 | 1.568 kHz | 45:32 |
| Perfect fifth | G♯6 | 1.661 kHz | 3:2 |
| Minor sixth | A6 | 1.76 kHz | 8:5 |
| Major sixth | A♯6 | 1.865 kHz | 5:3 |
| Minor seventh | B6 | 1.976 kHz | 9:5 |
| Major seventh | C7 | 2.093 kHz | 15:8 |
| Octave | C♯7 | 2.217 kHz | 2:1 |
Instruments and voices that can play C♯6
Frequently asked questions
What is the frequency of C♯6?
C♯6 is 1.109 kHz when A4 = 440 Hz (1.089 kHz if A4 = 432 Hz).
What MIDI number is C♯6?
C♯6 is MIDI note number 85.
Is C♯6 on a piano?
Yes – it is key 65 of 88.
Where is C♯6 on the guitar?
In standard tuning: 1st string (high E), fret 21.