396 Hz, 639 Hz and 963 Hz together: what the three share
396 Hz, 639 Hz and 963 Hz are three Solfeggio tones written with the same three digits, 3, 6 and 9, in turn. The Bible verse count behind the 1999 book that named 396 and 639 spells 963 as well. Played together the three sound smooth, since each sits about three of the ear's frequency bands from the next. No study has tested the trio itself.
Ready to play Release And Steadying 396 Hz
Leave room for a kinder thought about yourself.
What do 396 Hz, 639 Hz and 963 Hz have in common?
They are the same three digits in turn. 396, 639 and 963 each use 3, 6 and 9 once, and moving the first digit of one to the end gives the next: 396 becomes 963, 963 becomes 639, and 639 becomes 396 again. The digits of each add up to 18, and 1 + 8 makes 9.
Write the nine Solfeggio numbers in three rows and these three make the last column, as 174, 417 and 741 make the first. The guide to 174, 417 and 741 Hz works through that first column; this guide works through the last.
| First column | Middle column | Last column |
|---|---|---|
| 174 | 285 | 396 |
| 417 | 528 | 639 |
| 741 | 852 | 963 |
Tradition gives each of the three its own meaning. An early tuning-fork maker's list of the Solfeggio tones, kept by the Internet Archive, calls 396 Hz "Liberating Guilt and Fear" and 639 Hz "Connecting/Relationships". 963 Hz joined the set later and is often called the God frequency, as the 963 Hz guide explains. These meanings are tradition, not findings; the 396 Hz guide and the 639 Hz guide trace where each one came from.
Where do 396, 639 and 963 come from?
From verse numbers in the Bible. Healing Codes for the Biological Apocalypse, a 1999 book by Leonard Horowitz and Joseph Puleo, presented six numbers, 396 and 639 among them, as the missing tones of an old Solfeggio scale. The publisher's news release said its co-author, named there as Dr Joseph Barber, "was intuitively guided to find the pattern of six repeating codes in the Book of Numbers, Chapter 7, verses 12 through 83", decoded by "reducing the verse numbers to their single digit integers".
Numbers 7 lists the gifts twelve leaders brought, one leader a day, and each day opens six verses after the one before: verse 12, "the first day was Nahshon", verse 18, "On the second day Nethaneel", and so on to verse 78, "On the twelfth day Ahira". Add up the digits of each day's opening verse until one digit is left, and the twelve sums run 3, 9, 6, 3, 9, 6 to the end.
Read any three days in a row and you get one of three numbers. Starting on day 1, the sums spell 396. Starting on day 2, they spell 963. Starting on day 3, they spell 639, and then the run begins again. The book took 396 from these opening verses, and found its 639 in the fourth verse of each day: verses 15, 21 and 27 add up to 6, 3 and 9. The opening verses spell 639 as well.
963 was not one of the book's six. By late 2000 other sellers had moved from six numbers to nine, as one tuning-fork maker recalled under the heading "Why 6 forks when others have gone to 9?", and a 2007 trademark application in Horowitz's name lists nine numbers, 963 among them. Neither says how 963 was chosen. What the verse count shows is that the opening verses that give 396 spell 963 one day later, so all three numbers in this guide sit in one row of Numbers 7.
The pattern comes from counting in sixes, not from the words of the verses. Adding 6 to any number moves the sum of its digits from 3 to 9, from 9 to 6 and from 6 back to 3, so any count that steps by six from a number whose digits add up to 3 spells the same three numbers.
What happens when 396 Hz, 639 Hz and 963 Hz play together?
They make a wide, open chord with no two tones close together. 639 Hz is 1.614 times 396 Hz, an interval of 828.4 cents, a little over a minor sixth, where a cent is a hundredth of a semitone. 963 Hz is 1.507 times 639 Hz, 710.1 cents, just over a fifth. From bottom to top the chord spans 1,538.4 cents, an octave and a minor third and a little more.
| Pair | Interval | Bands apart |
|---|---|---|
| 396 and 639 Hz | 828.4 cents, past a minor sixth | 3.05 |
| 639 and 963 Hz | 710.1 cents, past a fifth | 2.95 |
| 396 and 963 Hz | 1,538.4 cents, past an octave and a minor third | 6.0 |
One of those ratios is close to a famous number: 639 over 396 is 1.6136, within 4.7 cents of the golden ratio, 1.618. That is a coincidence of the arithmetic, since the numbers come from adding up the digits of verse numbers.
All three numbers divide by 9: 396 is 44 nines, 639 is 71 and 963 is 107. So the three waves start together again every ninth of a second, every 111.11 ms, after exactly 44, 71 and 107 waves. In the mix of Harmonance's three tone files, the sound one third of a second later matches itself with a correlation of 0.99995.
Why do 396 Hz, 639 Hz and 963 Hz sound smooth together?
Because each one sits well clear of the others in the inner ear. Whether two plain tones sound smooth or rough depends on how far apart they are compared with the ear's critical band, the stretch of the inner ear that one tone sets moving. In a classic study, Plomp and Levelt found that listeners judged two plain tones consonant once they were more than a critical band apart, and most dissonant at about a quarter of a band.
By Glasberg and Moore's formula, 24.7 × (0.00437 f + 1), which hearing scientists use today, the band is about 81 Hz wide midway between 396 and 639 Hz, and about 111 Hz wide midway between 639 and 963 Hz. The gaps are 243 and 324 Hz, so each neighbouring pair sits about three bands apart, well into the smooth end of the scale.
On the ear's own scale the spacing is close to even. The same review gives that scale in units called Cams, 21.4 × log10(0.00437 f + 1), where "each 1-Cam step represents a distance of about 0.89 mm along the basilar membrane", the strip inside the inner ear that sorts sound by pitch. 396 Hz sits at 9.34 Cams, 639 Hz at 12.39 and 963 Hz at 15.34: steps of 3.05 and 2.95, or about 2.7 mm and 2.6 mm. In hertz the upper gap is a third wider than the lower; in the ear the two are nearly the same.
That smoothness belongs to where the tones sit, not to the history of the numbers: any three plain tones this far apart would sound as smooth.
Do 396 Hz, 639 Hz and 963 Hz beat?
The three tones do not, but two of their faint overtones do. Harmonance renders each tone with a little of its second and third harmonics, 23 and 34 dB below it. Of every pair of lines from different tones, two pairs share one band. 1,188 and 1,278 Hz, the third harmonic of 396 Hz and the second of 639 Hz, are 90 Hz apart: too fast to hear as beats, since beats that come more often than "roughly 20 or 30 times per second" are no longer heard as beats, as UNSW's physics pages on beats explain. The other pair is much closer.
The third harmonic of 639 Hz is 1,917 Hz, and the second harmonic of 963 Hz is 1,926 Hz: 9 Hz apart. They beat because 963 Hz is slightly more than a pure fifth above 639 Hz. A pure fifth is the ratio 3:2, which would put the upper tone at 958.5 Hz, and then both overtones would land on 1,917 Hz together. At 963 Hz they sit 9 Hz apart and beat 9 times a second, slow enough to count. It is the kind of beat a guitarist tunes away by ear, turning one string until its harmonic "stops beating" with another's, as the same UNSW pages show.
Measured in the mix, the level of the sound near 1,920 Hz rises and falls by about a third, 9.0 times a second. That band sits 22.8 dB below the tones, so the flutter is faint, at the top edge of the sound, and whether anyone notices it depends on the volume, the speakers and the listener. Plomp and Levelt traced the difference between consonant and dissonant intervals to exactly this kind of thing: "beats of adjacent partials".
The ear can also add faint tones of its own below a pair, called combination tones. The one heard most is twice the lower tone minus the higher: 153 Hz for 396 and 639 Hz, and 315 Hz for 639 and 963 Hz. In Goldstein's experiments its level "decreased sharply with increasing frequency interval", and these pairs are far apart, so it is faint at most. The plain difference tones, 243 and 324 Hz, were heard only at high levels, above 50 dB sensation level. The files themselves hold nothing at any of the four, as the chart below shows.
What is in Harmonance's 396 Hz, 639 Hz and 963 Hz tones?
The three pages each play a 20 second loop. Harmonance mixed the three files sample for sample, as if all three played at once, and measured every line in the result. The tones sit at 396.000, 639.000 and 963.000 Hz, within 0.01 dB of one another in level. Above each sit its two faint harmonics, and nothing else in the files comes within 57.8 dB of the tones.
| Line | What it is | Below the tones |
|---|---|---|
| 396 Hz | the 396 Hz tone | 0 dB |
| 639 Hz | the 639 Hz tone | 0 dB |
| 963 Hz | the 963 Hz tone | 0 dB |
| 792 Hz | second harmonic of 396 Hz | 23.2 dB |
| 1,278 Hz | second harmonic of 639 Hz | 23.1 dB |
| 1,926 Hz | second harmonic of 963 Hz | 23.1 dB |
| 1,188 Hz | third harmonic of 396 Hz | 34.0 dB |
| 1,917 Hz | third harmonic of 639 Hz | 34.0 dB |
| 2,889 Hz | third harmonic of 963 Hz | 34.0 dB |
| 153 Hz | not in the files: where the ear can add a tone | 97.2 dB, the noise floor |
| 243 Hz | not in the files: a difference tone's place | 81.4 dB, the noise floor |
| 315 Hz | not in the files: where the ear can add a tone | 79.4 dB, the noise floor |
| 324 Hz | not in the files: a difference tone's place | 83.7 dB, the noise floor |
Download the measurements (CSV)
So the pages play three near-pure tones at the same level, with overtones far enough down to stay in the background. Each tone also plays with Strings on its own page, where strings tuned to the tone carry the music and the exact tone sits underneath.
What do studies show about 396 Hz, 639 Hz and 963 Hz together?
No study Harmonance found has played these three together. The nearest is a small American study that played six Solfeggio tones, 396 Hz and 639 Hz among them, and then "a combination of all six frequencies" to 18 healthy adults while measuring skin conductance, the skin's readiness to carry a tiny current, which rises with arousal (Presley, Stamps and Davis Alexander, 2026). Each tone played for five minutes, always in rising order. Skin conductance fell a little with 396 Hz, "a slight, insignificant decrease", then rose with each tone after it, and the rises for 741 Hz, 852 Hz, the six together and the reading after the tones were significant.
Because the order never changed, the study cannot separate pitch from time: the combination came last, and the reading kept rising after the tones had stopped. The authors' own next step is "randomizing frequencies to account for sequential increases versus exposure". 963 Hz was not played at all.
Research on single Solfeggio tones is thin too. A 2026 review of music and tones after brain injury and stroke finds "little direct empirical evidence supporting these individual frequencies" (Whitney and colleagues, Cureus), and research on music as a whole is still young. The US National Center for Complementary and Integrative Health sums it up:
However, because much of the research on music-based interventions is preliminary, few definite conclusions about their effects have been reached.
So what is known about the three together is acoustics: why they blend, and where their one faint beat comes from. What they do for a listener has not been tested.
How do you listen to 396 Hz, 639 Hz and 963 Hz?
Press play at the top of this guide to hear 396 Hz, or open the 396 Hz page, the 639 Hz page and the 963 Hz page. Each plays its tone alone, or with Strings switched on. Nothing plays until you press play, and no account is needed.
To hear the three together, open Harmonance Studio, the free Harmonance instrument, which plays several tones at once after you sign in with a free account: add 396, 639 and 963 Hz, then balance them by ear. Bring them in one at a time, lowest first, and notice how the chord changes as each one arrives.
Keep the volume low either way: loud listening is the one risk that is well established. The NCCIH notes that "listening to music at too high a volume can contribute to noise-induced hearing loss", and the World Health Organization puts the safe limit for a level of 80 dB at 40 hours a week.
The Want to feel grounded page gathers 396 Hz with other tones people reach for, and the Feeling disconnected page does the same for 639 Hz. The Solfeggio collection plays all nine numbers, and the guide to the nine Solfeggio frequencies tells their whole story. For two tones heard together, 528 Hz and 432 Hz works through another pair.
Sources and limits
The arithmetic here can be redone by anyone with the verse list and a calculator, and the hearing science comes from classic papers. The research on the tones is thin: one small study played two of the three among six tones, always in the same order, and no study has played the three together. The measurements of the three tone files are Harmonance's own, made from the files the pages play.
- Horowitz and Puleo (1999), Healing Codes for the Biological Apocalypse, its Google Books record: the book that printed the six Solfeggio numbers.
- Tetrahedron Publishing, news release for the book, Internet Archive copy: the verse numbers of Numbers 7 and how they were read.
- Numbers 7, King James Version, on eBible: the twelve days and their opening verses.
- An early list of the six Solfeggio tones and their meanings, Internet Archive copy.
- A tuning-fork maker on six numbers or nine, Internet Archive copy.
- US trademark application 77099679 (2007), its USPTO record: nine numbers, 963 among them.
- Plomp and Levelt (1965), tonal consonance and critical bandwidth, in The Journal of the Acoustical Society of America: when tones sound smooth or rough.
- Moore (2014), the Cambridge loudness models, in Trends in Hearing: the width of the ear's filters and the ear's own scale.
- UNSW Physics, interference and beats: when beats stop being heard, the pure fifth, and tuning by harmonics.
- Goldstein (1967), auditory nonlinearity, in The Journal of the Acoustical Society of America: the tones the ear adds.
- Presley, Stamps and Davis Alexander (2026), pure tone Solfeggio frequencies and skin conductivity, in the Journal of Scientific Exploration: 18 adults, six tones and their combination.
- Whitney and colleagues (2026), music and tones after brain injury and stroke, in Cureus: the evidence for single Solfeggio tones.
- National Center for Complementary and Integrative Health, music and health: the state of the research, and loud listening.
- World Health Organization, safe listening: how long a level is safe.
Tones to play while you read
Related guides
111 Hz benefits and the ancient chamber story
111 Hz benefits, checked: the angel number behind the tone, the stone chambers that ring near 110 Hz, and what a pilot found when 30 adults listened.
141.27 Hz benefits: what the Mercury frequency is and is not
141.27 Hz benefits, checked: the Mercury tone is its 88-day orbit raised 30 octaves, its spin sounds the fifth above, and no study has tested it.
174 Hz benefits: the claims and what is known
174 Hz benefits, checked: the comfort and natural anaesthetic claims, where the number came from, and how 37 listeners rated the lowest Solfeggio tone.
Just be curious. This is not a medical device or medical advice. For any health concern, please speak to your doctor.