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

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.

Musical 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)

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.

musicequal-temperamentoctave-4