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C♯3 / D♭3 · 138.59 Hz

C♯3 is piano key 29 of 88 and MIDI note 49 - the low-mid register, around a male speaking and singing voice. Play the pure tone below, tune to it, or explore the note in every octave.

138.59Hz

Volume50%

Waveform

C♯3 at a glance

Frequency

138.59 Hz

Wavelength (in air)

2.47 m

MIDI note

49

Piano key

29 / 88

Octave

3

Enharmonic

D♭3

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 C♯3 is exactly 440 × 2^(-20/12) Hz. Under alternative references the note shifts with the reference: at A4 = 432 Hz, C♯3 becomes 136.07 Hz.

C♯ in every octave

Note	Frequency	MIDI	Piano key
C♯1	34.65 Hz	25	5
C♯2	69.30 Hz	37	17
C♯3 ←	138.59 Hz	49	29
C♯4	277.18 Hz	61	41
C♯5	554.37 Hz	73	53
C♯6	1108.7 Hz	85	65
C♯7	2217.5 Hz	97	77

Each octave doubles the frequency - the simplest relationship in music, and the reason notes an octave apart sound like “the same note, higher”.

Neighboring notes

B2 · 123.47 Hz C3 · 130.81 HzC♯3 · 138.59 HzD3 · 146.83 Hz D♯3 · 155.56 Hz

One semitone down is C3 at 130.81 Hz; one semitone up is D3 at 146.83 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.

C♯3 FAQ

What frequency is C♯3?

C♯3 / D♭3 is 138.59 Hz in twelve-tone equal temperament with the standard reference of A4 = 440 Hz. Every semitone step multiplies the frequency by the twelfth root of two (about 1.0595), and C♯3 sits 20 semitones below A4.

What MIDI number and piano key is C♯3?

C♯3 is MIDI note 49 and key 29 of 88 on a standard piano. Octave numbering follows scientific pitch notation, where middle C is C4 (MIDI 60).

How do I tune to C♯3?

Play the tone above and match your instrument by ear until the beating between the two pitches slows and disappears, or use the chromatic tuner with your microphone for a cents readout. Small mistunings show up as slow beats: one beat per second at this pitch means you are about 12.4 cents off.

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