C♯1 — 34.648 Hz
C♯1 (C-sharp 1) is 34.648 Hz in standard equal temperament at A=440 Hz. It is MIDI note number 25. This is the sharp spelling of this pitch — see also D♭1.
C♯ is the leading tone in D major and a key-signature accidental in all sharp keys from D major onward.
C♯1 Frequency in All Tuning Systems
| Temperament | Frequency (Hz) | Cents from Equal | Common Usage |
|---|---|---|---|
| Equal Temperament | 34.648 Hz | 0.00 | Modern standard; piano, fretted instruments |
| Pythagorean Tuning | 34.805 Hz | +7.83 | Medieval/early music; string ensemble open fifths |
| Just / Pure | 34.883 Hz | +11.70 | A cappella vocal, barbershop, Renaissance |
| Meantone 1/3 Comma | 34.298 Hz | -17.58 | Renaissance vocal music in minor keys |
| Meantone 1/4 Comma | 34.375 Hz | -13.69 | Renaissance keyboard, early Baroque organ |
| 1/6 SC - Attenuated | 34.455 Hz | -9.67 | Baroque orchestral ensemble compromise |
| Kellner's Bach | 34.687 Hz | +1.95 | Bach keyboard reconstruction |
| Kirnberger III | 34.658 Hz | +0.50 | Classical-era keyboard, keys near C major |
| Vallotti | 34.687 Hz | +1.95 | Baroque/Classical orchestral tuning |
| Werckmeister III | 34.687 Hz | +1.95 | Baroque keyboard; Bach contemporaries |
| Werckmeister IV | 34.531 Hz | -5.86 | Baroque keyboard, strong key contrast |
| Werckmeister V | 34.687 Hz | +1.95 | Specialized Baroque keyboard |
Positive cents = sharper than equal temperament. Negative cents = flatter. 100 cents = 1 semitone.
C♯1 at Different Concert Pitches
The same note varies in frequency depending on the concert pitch standard used by your ensemble.
| Concert Pitch | Frequency (Hz) | Common Usage |
|---|---|---|
| A = 440 Hz (ISO standard) | 34.648 Hz | US, UK, and most modern ensembles worldwide |
| A = 442 Hz | 34.805 Hz | Many European orchestras; France, Germany |
| A = 443 Hz | 34.884 Hz | Berlin Philharmonic; some US orchestras |
| A = 432 Hz | 34.018 Hz | Alternative tuning; Baroque revival |
| A = 415 Hz (Baroque) | 32.679 Hz | Historically-informed Baroque performance |
f = f_at_A440 × (concert_pitch / 440)
Instruments That Play C♯1
C♯1 (34.648 Hz) falls within the comfortable playing range of 3 instruments.
C♯1 and D♭1 — Enharmonic Equivalents
C♯1 and D♭1 are enharmonic equivalents — they sound identical at 34.648 Hz but are written differently depending on the musical context.
When to Write C♯1
C♯ is the leading tone in D major and a key-signature accidental in all sharp keys from D major onward.
Composers write C♯ when the harmonic context involves sharp keys — for instance, as the leading tone resolving up to D in D major, or as the 3rd of an A major chord. In ascending passages within sharp keys, C♯ is the correct spelling.
Major scales containing C♯1: D major (7th / leading tone), A major (3rd), E major (6th), B major (2nd), F♯ major (5th), C♯ major (tonic).
Minor scales containing C♯1: F♯ minor (5th), C♯ minor (tonic), G♯ minor (4th), B minor (2nd).
C♯1 in Instrument Literature
String instruments (violin, viola, cello) encounter C♯ frequently in sharp keys like D major and A major, which are natural keys for bowed strings. Guitarists use C♯ in keys like A and E major.
In fixed-do solfège, C♯ is sung as "di" (♯1). In D major with moveable do, it is "ti" (the leading tone).
How D♭1 Differs in Context
While D♭1 sounds identical to C♯1, it belongs to a different set of keys and carries different harmonic implications.
D♭1: D♭ is the tonic of D♭ major (5 flats) and appears as a scale degree in several flat keys.
Major scales: D♭ major (tonic), G♭ major (5th), A♭ major (4th).
Minor scales: B♭ minor (3rd), F minor (6th), E♭ minor (7th).
Wind and brass players encounter D♭ frequently. B♭ instruments (clarinet, trumpet) read it in their common flat-side keys, and French horn parts in flat keys use it regularly.
Enharmonic equivalents share the same frequency in equal temperament. In historical temperaments like Pythagorean or meantone, they may differ slightly — see the temperament comparison table above for this note's exact deviations.
Why C♯1 Varies Across Tuning Systems
C♯1 shows a maximum deviation of -17.58 cents in Meantone 1/3 Comma compared to equal temperament. This 18-cent difference is clearly audible to trained musicians and reflects how different tuning philosophies prioritize interval purity over equal distribution.
In Meantone 1/3 Comma, C♯1 is tuned flatter than equal temperament, reflecting this system's approach to distributing the Pythagorean comma across the chromatic scale.
3 of the 15 non-equal temperaments deviate by more than 10 cents for C♯1, making this note one where tuning system choice has a meaningful impact on pitch.
C♯1 Across All Tuning Systems
Explore how C♯1 is tuned in each historical temperament system. Each tuning system gives C♯1 a slightly different frequency, affecting the harmonic character of chords and melodies.
C♯1 in Historical Temperament Systems
Explore how C♯1 (34.648 Hz in equal temperament) is tuned in each of the 15 historical non-equal temperament systems. Each system places C♯1 at a slightly different frequency based on its mathematical basis.
Tune C♯1 with precision — Get Tunable.
Tunable supports 15+ tuning systems including equal temperament, Pythagorean, just intonation, and historical well-temperaments. See exact Hz values in real-time as you play.
