A4 = 440 Hz: the international tuning standard and how to tune by ear
By TechCompare · Updated · How we check
A4 = 440 Hz is the international standard tuning reference. Play a 440 Hz sine tone and match your A string to it, then tune the rest by interval. When you're close, the beat frequency gives you your final adjustment.
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A4 = 440 Hz is the international standard tuning pitch, also called concert pitch or A440. The A above middle C tuned to 440 Hertz is the reference most orchestras, tuner apps, and instruments use. Playing a 440 Hz sine tone gives you a clean reference to tune to: no harmonics, no overtones, just the pitch itself.
How this is calculated
Concert pitch wasn't always 440 Hz. Before the 20th century, pitch varied by region and ensemble, often somewhere between 415 Hz (Baroque) and 456 Hz (some military bands). The 440 Hz standard emerged in the early 1900s and was adopted by the International Organization for Standardization in 1955.
Some orchestras today tune a little above 440 Hz. The Berlin Philharmonic famously uses A = 443 Hz for a brighter sound, about 11.8 cents above standard pitch. But 440 remains the reference for sheet music, electronic instruments, and most music education.
To tune by ear, play the 440 Hz tone and match your A string to it. Once your A is in tune, tune the rest of your strings by interval or harmonic. Use the beat frequency method for the final adjustment: when your string is close to 440, any remaining difference shows up as a slow beat.
Verdict
Tune your A string to a 440 Hz sine, since a clean tone without overtones is the easiest reference to match by ear. The standard is a 1955 convention, but sheet music, electronic instruments, and most music education use it, so it's worth learning.
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Frequently asked questions
Why is A4 tuned to 440 Hz?
Do all orchestras tune to 440 Hz?
How do I tune a guitar by ear to A440?
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