Instrument Resonances
Tuning Fork — A440 (Concert Pitch)
440.00 Hz
Note: A4
Cosmic Octave Color
Derived visible color (620 nm)
Display swatch #e9852d
EstablishedInstrument / Acoustic Reference
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 describes an instrument or resonance reference. Therapeutic outcomes depend on context, level, instrument build, and listener response.
Review the evidence modelThe modern international standard for concert pitch. A4 = 440 Hz was established by ISO in 1975. Used to tune all orchestral instruments. Some musicians advocate for A432 instead.
Wavelength
78.0 cm
Nearest Note
A4 (0¢)
Claim Type
Instrument / Acoustic Reference
Cosmic Octave Color
Derived visible color (620 nm) · #e9852d
Source
ISO 16 (1975)
Sources
ISO 16
1 atlas references
International standard specifying concert pitch reference for A4.
ISO 16: Standard tuning frequency (A4 = 440 Hz).
Historical Use
International concert pitch standard since 1939 (unofficial), ISO standard since 1975
instrumenttuning-forkconcert-pitchstandard