Tuning Fork — A440 (Concert Pitch)
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.
Sources
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
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.