What Is A440? Concert Pitch and Reference Frequency Explained

Almost every tuner on Earth defaults to A4 = 440 Hz: the A above middle C vibrates 440 times per second, and every other note is derived from it. But that number is a convention, not a law of physics — and it has a surprisingly contentious history.

A short history of concert pitch

Before standardization, pitch varied wildly from city to city. Surviving 17th- and 18th-century organs and tuning forks show "A" anywhere from about 390 Hz to well over 460 Hz. A singer touring Europe might face a semitone difference between venues.

The 19th century brought attempts at order — France legislated A = 435 Hz in 1859 — and in 1939 an international conference settled on A = 440 Hz, reaffirmed by ISO 16 in 1955. Broadcasting made it stick: the BBC even transmitted a 440 Hz tone as a tuning reference.

Why do some orchestras tune higher?

Many European orchestras tune to A442 or even A443 — a slightly higher pitch adds brilliance and projection to the string sound. If you play along with such recordings, set the reference in our tuner to match (the A4 box accepts 400–480 Hz).

Baroque pitch: A415

Period-instrument ensembles typically use A = 415 Hz — roughly a semitone below modern pitch — reflecting the instruments and evidence of Bach's era. Gut strings and historical winds behave better there.

What about "432 Hz"?

You may have seen claims that A432 is "natural" or "healing". There's no scientific evidence for special properties of 432 Hz — it's simply another reference pitch, one of many used through history. If you enjoy the slightly mellower sound, our tuner happily supports it; just don't expect miracles.

Practical takeaways

• Tuning alone or with others using the same tuner? Leave it at 440.
• Playing with a piano or accordion? Match them — fixed-pitch instruments win.
• Playing along to a recording that sounds "in the cracks"? The band may have tuned down, or tape speed shifted the pitch — adjust your reference until it matches.