What Is A440 Tuning? The Standard Pitch Explained

What is A440 tuning? It is the standard pitch reference in which the A above middle C (A4) vibrates at 440 Hz, and every other note is tuned relative to it. Most tuners, instruments, sample libraries and recordings assume A440, so matching it keeps you in tune with the rest of the world. To hear the reference, play A440 or any other note in the free online tone generator.

Why a pitch standard exists

A note name like “A” does not describe a fixed sound on its own. Without an agreed reference, two instruments can both play an A that sounds noticeably different. A pitch standard fixes one note to a frequency so pianos, guitars, synths and orchestras can play together. A440 was adopted as an international standard and is described in ISO 16; it is the default in almost every electronic tuner and DAW.

How the other notes are calculated

Modern Western music uses twelve-tone equal temperament. Each octave doubles the frequency, and the octave is split into twelve equal semitone steps, so each semitone multiplies the frequency by the twelfth root of two (about 1.0595). Starting from A4 = 440 Hz:

Note	Frequency at A440	Common use
A2	110.00 Hz	Guitar 5th string
E2	82.41 Hz	Guitar low E string
C4 (middle C)	261.63 Hz	Piano reference
A4	440.00 Hz	Tuning reference
A5	880.00 Hz	One octave above A4

To look up any note, frequency or MIDI number, use the pitch to Hz and MIDI converter.

A440 vs A442 vs A432

A440 is the common default, but you will meet other references:

• A442 and A443. Some orchestras tune slightly higher for a brighter sound. If you record with an orchestra or a piano tuned this way, set your tuner and virtual instruments to match.
• A432. This places A about 32 cents lower than A440. Some musicians prefer it, but there is no scientific evidence that it sounds better or has special effects on the listener. It only matters that everyone on a recording uses the same reference.
• Historical pitch. Early-music ensembles often use lower references, such as A415, to match period instruments.

In the tone generator you can change the A4 reference to 442 Hz, 432 Hz or any value, and every note updates to that tuning.

How to tune to A440 with a tone generator

1. Turn your speakers or headphones down first, then raise the level gently. Pure tones can be tiring, especially on headphones.
2. Choose the A440 preset, or select the note you want to match.
3. Play your instrument’s note at the same time and listen for a slow wobble, called beating. Beating means the two pitches are slightly different.
4. Adjust the instrument until the wobble slows and disappears.
5. For a guitar, play the Low E preset (82.41 Hz), tune that string, then work through A2, D3, G3, B3 and E4.

The tool fades every tone in and out, caps the output well below full scale and stops after five minutes or when you switch tabs, so it is safe to leave a reference running while you tune.

Other uses for a tone generator

• Checking speakers and headphones. Sweep through low frequencies to hear where your monitors stop producing bass, or find rattles in the room.
• Ear training. Play a reference and sing or hum the note, then check whether you landed on it. Our guide on ear training for audio engineers builds on this.
• Tuning samples. Play the tonic of your song as a sine tone and tune a kick, 808 or vocal chop until it sits with it.
• Testing your hearing range. The upper limit of what you can hear drops with age and noise exposure. For a structured check, use our online hearing test.

Does tuning reference matter in a DAW?

Inside a DAW most synths and samplers follow a master tune setting, usually A440 by default. If you record a live instrument tuned to something else, either retune the instrument or change the master tune so the virtual instruments match. Mismatched references produce parts that sound slightly sour together even when every note is “right”. A sung vocal can be checked against the reference with our vocal tuner.

Cents, beating and how close is close enough

Tuning differences are measured in cents. One cent is a hundredth of a semitone, so an octave contains 1,200 cents. Small offsets are hard to hear on a single note but become obvious when two notes play together, because the slight difference in frequency creates beating: a regular pulse in volume. The beat rate equals the difference between the two frequencies, so a note at 441 Hz played against 440 Hz pulses once per second. As you get closer, the pulse slows, and when it stops the two pitches match.

The tone generator’s fine-tune slider moves a note in cents, which is useful for matching an instrument that is consistently a little sharp or flat, such as an old piano you cannot retune before a session. Set the generator to the instrument’s pitch, then tune the rest of the band to that reference.

Common mistakes

• Starting a tone at high volume. Always begin low, especially on headphones.
• Mixing references on one session. A piano at A442 and a synth at A440 will clash.
• Tuning by octave confusion. Make sure you are matching the same octave, or a clean octave above or below.
• Expecting A432 to fix a mix. Changing the reference does not improve tone or balance; arrangement and mixing do.

FAQ

For more ways to sharpen your hearing, see our ear training guide and the background on the A440 pitch standard. Need a reference note right now? Open the free tone generator and press play.