What Is 432 Hz? What It Does and How It Compares to 440

432 Hz is a tuning frequency a third of a semitone below standard pitch. What the studies found, how it compares to 440, and how to hear it.

432 Hz is a way of tuning music. The note A above middle C sits at 432 hertz instead of the usual 440, so the whole song plays a little lower, by about a third of a semitone. In the studies so far, 432 Hz music calms people about as well as the same music at 440. The calm comes from the music itself.

So if a 432 playlist helps you wind down, keep playing it.

What is the 432 Hz frequency, exactly?

It's a tuning, not a tone. Every instrument in a band tunes to one reference note, the A above middle C, and the standard puts it at 440 Hz. Tune that A to 432 instead and every other note moves down with it.

The gap is 31.8 cents, which is 1.8 percent in frequency. The whole song shifts by that amount, so every chord and melody keeps its exact shape. Nothing sounds out of tune. It just sits slightly lower.

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Where does 432 Hz come from?

The number comes from arithmetic. Set middle C at 256 Hz, a power of two, climb a Pythagorean major sixth, and you land on 432 exactly. That's where its "mathematical" reputation comes from. In equal temperament, the tuning nearly all music uses, the same climb from C lands on 430.5.

The fight over pitch is much older than the number. Concert pitch used to change from town to town: German organs before 1600 ranged from A = 377 to A = 567. In the 1800s opera houses kept tuning higher, and singers strained to keep up. France set A at 435 by law in 1859. Giuseppe Verdi was the loudest voice against rising pitch, and in 1881 he sent the composer Arrigo Boito to argue the case at a congress of Italian musicians in Milan. That's why Verdi's name comes up in every 432 thread.

Then the standard was settled. In May 1939, delegates from France, Germany, Britain, Holland and Italy met at the BBC's Broadcasting House in London and agreed on 440. Nature reported it that year, and it became the international standard, ISO 16.

The push for 432 began almost fifty years later, in Verdi's own house. On April 9, 1988, at a Schiller Institute conference at Casa Verdi in Milan, singers launched a campaign to return to "Verdi's tuning": A at 432, from C at 256. Dietrich Fischer-Dieskau and Birgit Nilsson signed its petition, and Renata Tebaldi spoke for it. Their reason was voices. A lower pitch spares singers the strain of the high notes.

The darker version of the story came three years later. A 1991 essay from the same campaign claimed that Joseph Goebbels organized the 1939 conference. Its only evidence is that a Berlin radio committee asked for the meeting to take place. The conference itself was organized by the British Standards Institution.

The whole history, from the organ pitches to the trials, is in A Third of a Semitone.

What are the benefits of 432 Hz music?

Most 432 trials compare 432 music with silence, and the music wins, as music usually does. Four trials played the same music at 432 and at a standard tuning.

The study everyone cites

In a listening room in Tuscany, 33 volunteers heard 20 minutes of film music on two different days. One day it was tuned to 440, the other to 432. After the 432 session, their heart rates had dropped by 4.79 beats per minute, and after the 440 session by less than one.

That's the number you'll see on most 432 pages. But each session was measured against its own starting point, and the two drops were never tested against each other. The 432 version was also made by slowing the recording down, so it played slower too. Tempo is one of the strongest drivers of how the heart responds to music.

The dentist's waiting room

In Chile, 42 people waiting to have a tooth pulled were split into three groups: 15 minutes of 432 music, the same music at 440, or silence. Both music groups ended up about half as anxious as the silent group, and the two tunings scored almost the same (8.7 against 8.4).

The 432 group did end with lower cortisol, the stress hormone. That group also started with about half the cortisol of the others. Once the researchers allowed for where each group began, 432 and 440 came out the same.

Strings on the chest

A German trial put a monochord, a wooden box strung with 29 strings, on cancer patients' chests and played it tuned to 432 or to 443. Heart rate fell further under 432, and more patients preferred it. When the researchers compared the two tunings directly, the gaps in blood pressure, heart-rate variability and arterial stiffness were too small to count.

The warm-up

A Tunisian team had 22 athletes warm up to their own favorite music, once at 440 and once at 432. They ran faster and jumped higher after the 440 warm-up. Music helped at either tuning.

In all four, music helped and 432 gave no extra benefit you could count on. A Cochrane review of 26 trials found the same about music in general: listening lowers anxiety while people wait for a procedure.

432 Hz vs 440 Hz: can you hear the difference?

Side by side, yes. Of the 33 people in the Tuscan study, 32 noticed the two sessions sounded different. Almost half thought the 432 session was louder, and 23 of the 33 preferred the sound of the 440 session.

Without the comparison, it's much harder. Every note moves together, so nothing in the song sounds off.

Trevor Cox, a professor of acoustic engineering at the University of Salford, put it to a listening test. About 200 people compared 1,396 pairs of clips at seven tunings, from 416 to 465 Hz. Raising the pitch made music less liked, and lowering it changed nothing: 432 and 440 were liked equally.

How to try 432 Hz music

To hear it for yourself, compare the same song both ways.

Pick a calm song you know well.
Open it in a free audio editor such as Audacity and choose Effect > Pitch and Tempo > Change Pitch.
Lower the pitch by 0.32 semitones and save it as a copy. Change Pitch keeps the tempo, so only the tuning moves.
Set both versions to the same volume.
Ask someone to play them to you in a random order, and see if you can pick the 432 one.

After that, choose music by how it makes you feel, at whatever tuning it comes in.

This is Watershed, from Lissa: a sound bath of singing bowls and soft, distant voices, with an Alpha beat underneath. Headphones on first.

Questions people ask

What does 432 Hz actually do?

It lowers the pitch of a song by about a third of a semitone. Music at 432 relaxes people, and so does the same music at 440. In the trials that compared the two, the tuning made no reliable difference.

Which is better for healing, 432 Hz or 440 Hz?

Neither has been shown to heal anything. Music at either tuning lowered anxiety in the trials, and 432 added nothing on top.

Why do we use 440 instead of 432?

Orchestras needed one shared pitch so instruments from different places could play together. A conference in London picked 440 in 1939, and the ISO made it the international standard.

How long should you listen to 432 Hz?

As long as you enjoy it. In the trials, 15 to 20 minutes of music was enough to lower anxiety and heart rate.

Is listening to 432 Hz safe?

Yes. It's ordinary music, a little lower in pitch. Keep the volume moderate, as with anything you listen to for a long time.

Is 432 Hz good for sleep?

The 432 trials didn't test sleep. Pick the calm music you like best before bed, at whichever tuning it comes in.

The full research, with every trial and its numbers, is in A Third of a Semitone. For sound baths and time set aside for yourself, see Heal.