Concert Pitch Reference — A=440, 432, 442, 443, 415 Hz

Concert Pitch Standards

A Brief History of Concert Pitch

Before the 20th century, concert pitch was not standardized internationally. From roughly 1600 to 1850, the A4 reference frequency varied widely across Europe — from approximately 380 Hz in some Baroque contexts to as high as 465 Hz in certain 18th-century German and Austrian cities. Surviving instruments from different periods and regions reflect this variation: Baroque woodwinds, natural trumpets, and organs built in the same century but different countries often differ by a semitone or more in their intended pitch level.

Attempts at standardization began in the 19th century. The Stuttgart conference of 1834 proposed A=440 Hz, but the proposal was not widely adopted. France standardized at A=435 Hz in 1858 (the diapason normal), which was endorsed by various European governments and used widely in opera and conservatory contexts through the late 19th century. Britain, Germany, and the United States each maintained different conventions, making international ensemble coordination difficult.

The decisive modern standardization came at the 1939 London international conference on pitch standardization, where A=440 Hz was adopted as the international reference. This was confirmed by ISO 16:1975, which remains the current international standard. The choice of 440 Hz reflected a compromise among existing practices and the practical needs of instrument manufacturers and broadcasters.

In modern practice, orchestras routinely tune above 440 Hz despite the ISO standard. European orchestras have trended progressively higher through the 20th century — many German, Austrian, and Dutch ensembles use A=442 Hz, while some orchestras in Europe and Asia use A=443 Hz or higher. The early music movement, beginning in the mid-20th century, revived the study of historical pitch levels, leading to the establishment of A=415 Hz as the standard for historically-informed performance (HIP) of Baroque music.

The practical effect of this range — from A=415 Hz in Baroque HIP to A=445 Hz in some modern ensembles — is a span of approximately 110 cents, nearly a full semitone. Instrumentalists who perform across periods and traditions must be prepared to calibrate to different reference frequencies, and fixed-pitch instruments must be tuned or built to the specific standard required.

How Concert Pitch Affects All Notes

In equal temperament, every note frequency is derived from the A4 reference using the formula f = A4 × 2^{(MIDI − 69) / 12}. This means that changing concert pitch shifts all 12 chromatic notes proportionally. The ratio between any two notes remains identical regardless of concert pitch — only the absolute Hz values change.

For example, C4 at A=440 Hz is 261.626 Hz. At A=432 Hz, C4 shifts to 256.869 Hz — the same ratio of C4/A4 (2^−9/12 ≈ 0.5946) is preserved, but both notes are scaled down by the factor 432/440 ≈ 0.9818. Every instrument in an ensemble must use the same concert pitch reference for these ratios to produce the expected harmonic relationships between parts.

Related Reference Pages

• A4 note — frequency data across all temperaments
• Note frequency hub — all 153 notes