432 Hz tuner

By Daniel Breyer, physicist and one half of Acado, Berlin. He studied theoretical quantum physics, published in Physical Review A, and has made club music as Acado for twenty years.

The strings in Hz

The guitar's strings at A4 = 432 Hz and, for comparison, at 440 Hz.

Tuning to A = 432 Hz

Tap start and play one note. The tuner names the nearest note with A4 at 432 Hz, shows the Hz it hears and how many cents you are above or below, and ticks at five cents or closer. The Guitar switch asks for the six strings one at a time, E2 at 80.91 Hz up to E4 at 323.63 Hz. The switch under the needle moves the reference to 440 or 442 Hz: an A at 432 then reads about 32 cents low. The notes between the A's are equal temperament, as on a piano or a fretted guitar, so with A at 432 Hz the C below it is 256.87 Hz, not 256. Nothing is recorded; the microphone is read in the tab and closed when you stop.

432 Hz is 8 Hz below 440: 1.8 % lower, 31.8 cents, a little under a third of a semitone. Every note moves by the same ratio, so the intervals, the chords and the melody stay exactly what they were. The whole piece just sits a third of a semitone lower. Play both A's at once and you hear them beat, eight times a second, which is the difference between them. Two tools beside this one: the 432 Hz converter lowers a song you already have, and the 432 vs 440 test asks your ears, blind, whether they can tell.

Where 432 comes from

In the 19th century every city tuned its own A, and it kept creeping up, because a higher A makes an orchestra sound brighter and costs the singers their voices. France fixed its diapason normal at A = 435 in 1859. Verdi backed 435 at first and later argued for 432 as easier on singers; in 1881 he sent Boito to a congress of Italian musicians in Milan to make the case, and an Italian decree of 1884 prescribed 432 for orchestras and military bands. A year later the Vienna conference of 1885 voted for 435 across Europe, and Italy's 432 never spread.

The arithmetic behind 432 is older. In 1713 the French acoustician Joseph Sauveur proposed fixing middle C at 256 Hz, which is 2 to the power 8: every C becomes a power of two (1, 2, 4 … 128, 256, 512 Hz). This is the scientific or philosophical pitch. Build A on that C the way Pythagoras would, three pure fifths up and one octave down, and you get 27/16 of 256, exactly 432 Hz. In equal temperament, where every semitone is the same ratio, the same C = 256 gives A = 430.54 Hz instead, and A = 432 gives C = 256.87. Both numbers can be round at once only in one tuning system, and it is not the one pianos and guitars use.

440 won in the 20th century: an international conference in London agreed on it in 1939, and it became the standard ISO 16 in 1955, confirmed in 1975. Many European orchestras today tune a little higher, to 442 or 443.

The Schumann resonance, and why 7.83 is not 8

The Schumann resonance is real. Lightning, about fifty strikes a second somewhere on Earth, rings the gap between the ground and the ionosphere like a bell, and the lowest mode sits at about 7.83 Hz, with more at about 14, 20, 26 and 33 Hz. Winfried Otto Schumann predicted it in 1952, it was measured clearly from 1960, and today it is used to follow lightning around the globe. A perfect cavity the size of the Earth would ring at 10.6 Hz; the leaky ionosphere pulls it down, and it drifts with the time of day and the sun.

The 432 story rounds 7.83 to 8 and then notes that 8 × 54 = 432. But 54 is 2 × 27, not a power of two, so 432 Hz is not an octave of 8 Hz, it is not a note that 8 Hz contains, and any number divisible by 8 would do as well (440 is 8 × 55). The octaves of 8 Hz are 256 and 512; the octaves of the real 7.83 Hz are 250.6 and 501.1, and neither is a note of either tuning. It is also not sound: the Schumann resonance is an electromagnetic wave about 38,000 km long, and air does not carry it to your ears.

What actually changes a third of a semitone down

The pitch. Heard alone, most people cannot tell a song at 432 from the same song at 440; side by side, nearly everyone hears that one is lower. People with absolute pitch hear it straight away, and they are rare.

The strings. A string's tension goes with the square of its frequency, so at 432 every string carries 3.6 % less: a little slacker, a little easier to bend, a little quicker to buzz. Some players hear that as warmer. The body of the instrument and the room keep their own resonances, so the balance of the overtones shifts slightly; that part is real and small.

Playing with others. Everyone has to be at the same A. A piano needs a tuner to come down 32 cents, a harmonica, an accordion or a glockenspiel can't come down at all, and for a flute or a clarinet it is a long pull that puts its own notes out of tune with each other. Keyboards and synths have a master tune setting that does it in a second. So 432 works best alone, in a band that agrees on it, or with a recording that is also at 432.

Recordings. Almost everything you hear was recorded near 440. Many “432 versions” online are those recordings shifted down afterwards: slowed by 1.8 %, which turns four minutes into 4:04, or pitch-shifted, which keeps the tempo and processes the sound. To play along with a 440 recording, stay at 440.

Your body. A handful of small studies, a few dozen listeners each, report a heart rate a beat or two lower with music at 432 than at 440, and none can say whether that comes from the tuning or from the music and the setting. There is no evidence that 432 heals anything or that 440 harms. Whether 432 sounds better to you is your call, and this tuner gets you there.

To hear both A's, the tone generator plays any frequency; to name a sample's note at 432, the pitch detector has the same switch. The note frequency chart has every note in Hz.

The notes you tuned go into Brumm as a short melody over a beat.