Musical Frequencies
C#4
277.18 Hz
Note: C#4
Cosmic Octave Color
Derived visible color (492 nm)
Display swatch #0cc0d7
EstablishedMusical Standard
Evidence Level
Established
Source Count
1
Last Reviewed
March 23, 2026
Directly measured, standardized, or well-supported in mainstream scientific or technical literature.
This entry documents a musical reference or standard. It should be read as an acoustic and musical reference rather than a biological claim.
Review the evidence modelMusical note C# in octave 4. Mid to treble range.
Period
3.61 ms
Wavelength
1.24 m
Nearest Note
C#4 (0¢)
Claim Type
Musical Standard
Cosmic Octave Color
Derived visible color (492 nm) · #0cc0d7
Source
Equal temperament tuning system (A4 = 440 Hz)
Sources
Equal Temperament Tuning System
108 atlas references
The twelve-tone equal temperament reference used for note-frequency lookups throughout the atlas.
Standard equal-temperament note table with A4 = 440 Hz.
Harmonic Series
Octave Ladder
Every audible octave of this frequency — the same tone, higher and lower.
Nearby in the Atlas
Entries within ±35 cents of this tone when reduced to the same octave — candidates for pairing or comparison.
C#3Musical Frequencies
138.59 Hz0¢
C#5Musical Frequencies
554.37 Hz0¢
C#6Musical Frequencies
1.1 kHz0¢
C#7Musical Frequencies
2.2 kHz0¢
C#8Musical Frequencies
4.4 kHz0¢
C#1Musical Frequencies
34.65 Hz+0.1¢
musicequal-temperamentoctave-4