TL;DR
440 Hz is the reference pitch for the A above middle C. It was agreed at an international conference in 1939, adopted by ISO as a recommendation in 1955 and as a standard in 1975. Many orchestras tune slightly higher.
432 Hz is an alternative tuning about a third of a semitone lower. In 1884 Verdi said he would gladly accept it. Many of the claims made for it online, like healing, have no evidence behind them.
Seven small studies have compared music at the two tunings directly. A few results lean toward 432 Hz, such as slightly lower heart rate. Two studies of athletes favored 440 Hz.
Solfeggio frequencies (528 Hz and the rest) are a different idea: a modern list of individual tones, not a tuning. Research on them is limited too.
Neither tuning is proven to heal anything. If one sounds better to you, that's a fine reason to listen to it.
Search "432 Hz" and you'll find hours of music calling it the frequency of the universe, and comment threads insisting that standard 440 Hz tuning was chosen to make people anxious. Other people call the whole thing nonsense.
Both sides are arguing about a gap of 8 hertz. This post covers where each number came from, what the small amount of research actually found, and where Solfeggio frequencies fit in, since the two get mixed up constantly.
First, what 440 Hz actually is
Musicians playing together have to agree on where their notes sit. The convention is to pick one note, the A above middle C, and give it a frequency. Every other note is tuned relative to it.
For most of music history there was no single answer. Pitch varied from city to city and century to century. Ensembles playing period instruments today usually tune their baroque repertoire to about 415 Hz. In the mid-1800s France made 435 Hz its official A, and many other countries followed.
440 Hz isn't new either. German scientists recommended it as early as 1834. In 1939, delegates from several European countries met at the BBC's Broadcasting House in London and agreed on 440 Hz as a shared standard. The International Organization for Standardization adopted it as a recommendation in 1955 and as the standard ISO 16 in 1975.
Even now, 440 Hz is a reference, not a rule. Orchestras in continental Europe commonly tune anywhere from 440 to 444 Hz, and professional orchestras in Germany typically use 443 Hz.
Where 432 Hz comes from
432 Hz has a real history, and it's older than the internet.
In 1884, the composer Giuseppe Verdi wrote to an Italian government commission on pitch. He backed the French standard of 435 Hz, and said he would gladly go along with a slightly lower 432 Hz if the commission chose it. Many musicians at the time were unhappy that pitch kept creeping upward.
A related idea, "scientific pitch," sets middle C at exactly 256 Hz, which puts A at about 430.5 Hz. From the 1980s, the Schiller Institute campaigned for an A of 432 Hz, which it called "Verdi tuning."
The bigger claims came later: that 432 Hz is "the frequency of the universe," that it's in tune with the Earth, or that it heals the body. None of those comes with evidence.
You'll also see a story that 440 Hz was imposed by the Nazi propaganda minister Joseph Goebbels. There's no record of that. The 1939 meeting was an international standards conference in London, and German scientists had recommended 440 Hz more than a century earlier.
How different do they actually sound?
Not very. 432 Hz is about 32 cents below 440 Hz, roughly a third of a semitone. Played back to back, the 432 Hz version sounds slightly lower.
In a 2025 German study, patients had a monochord, a stringed instrument, placed on the chest and played live, tuned to 432 Hz in one session and 443 Hz in the other. 28 of 43 said they noticed a difference. Asked which they preferred, 24 chose 432 Hz, 6 chose 443 Hz, and 13 liked both equally.
What the research says
We found seven studies that directly compared music at 432 Hz with music at standard pitch (440 Hz, or 443 Hz in one case).
2019, 33 healthy volunteers (Italy). The same film soundtracks at both tunings, 20 minutes each. Heart rate was about 5 beats per minute lower with 432 Hz, a result right at the edge of statistical significance. Differences in blood pressure and breathing rate weren't significant. Listeners said they felt somewhat more focused and satisfied with 432 Hz.
2020, 12 patients with spinal cord injuries (same Italian team). Each listened to their favourite music at both tunings. Sleep scores improved with 432 Hz and not with 440 Hz. Stress didn't change significantly with either.
2020, 42 dental patients (Chile). Before a tooth extraction, patients heard 15 minutes of music at 432 Hz, music at 440 Hz, or no music. Both music groups were much less anxious than the no-music group, and their anxiety scores were about the same. The 432 Hz group had lower levels of cortisol, a stress hormone, in their saliva.
2022, 54 emergency nurses (same Italian team). During their break, nurses heard music at 440 Hz, music at 432 Hz, or took an ordinary break. Anxiety scores fell in all three groups, including the one with no music. Only the 432 Hz group showed a drop in breathing rate and in systolic blood pressure (the top number).
2025, 43 cancer patients (Germany, a different team). A 15-minute live session with a monochord placed on the chest, tuned to 432 Hz or 443 Hz. Both improved how people said they felt. Heart rate dropped a little more with 432 Hz (a median of 3 beats per minute versus 1). Most other differences between the two tunings weren't significant, and the authors called the comparison exploratory.
2025, 28 kickboxers. During a warm-up, athletes heard their preferred music at 440 Hz, the same music at 432 Hz, or no music, then ran a speed test. Both music conditions beat no music, and the 440 Hz version gave the fastest times and the best mood ratings.
2025, 22 male athletes (same team as the kickboxer study). The same design with sprint and jump tests. Music at either tuning helped compared with none, and the authors found the benefits more noticeable at 440 Hz.
Some of these results lean toward 432 Hz and two lean toward 440 Hz, and that's worth saying plainly. Look at the shape of the evidence: seven small studies, five of them from two research groups, short sessions, and different outcomes in each. In the dental study, anxiety fell about equally with either tuning, and in the nurses' study it also fell with an ordinary break. Nothing here shows 432 Hz healing anything. The fair summary is "early, small, and mixed," not "proven."
Where Solfeggio frequencies fit in
Solfeggio frequencies often get lumped in with 432 Hz, but they're a different idea. 432 versus 440 is about tuning: where you set the A, which shifts every note in a piece of music. Solfeggio frequencies are individual tones, most often listed as nine: 174, 285, 396, 417, 528, 639, 741, 852 and 963 Hz.
The name borrows from real history. In the 11th century, the monk Guido of Arezzo used a Latin hymn, "Ut queant laxis," to teach singers the scale. Each line began one note higher, and its first syllables gave us ut, re, mi, fa, sol, la (ut later became do). Those syllables named steps of a scale. They weren't frequencies.
The frequency list itself is modern. It's credited to Joseph Puleo, who is said to have worked the numbers out from Bible verses in the mid-1970s, and it spread through Leonard Horowitz's 1999 book Healing Codes for the Biological Apocalypse. Lists vary from six tones to nine.
We covered the most famous one in What Is 528 Hz? The short version: the best-known claim, that 528 Hz repairs DNA, doesn't come from studies. Research on Solfeggio tones is limited. A 2026 trial in Turkey played 528 Hz music, 432 Hz music or silence to 162 students before exams. It found differences in some saliva markers but none on a concentration test, and the authors called it hypothesis-generating.
One detail we like: Solfeggio tones don't line up with either tuning. In standard 440 Hz tuning, 528 Hz sits a little above C. In 432 Hz tuning, it lands almost halfway between C and C sharp.
The honest summary
440 Hz is a convention, agreed so musicians and broadcasters could match. 432 Hz is an older alternative with a real history and a small set of early studies, some leaning its way and some not. Neither is the "natural" frequency of anything, and neither is proven to heal. Solfeggio frequencies are a separate, modern list with little research behind them.
If music at 432 Hz sounds warmer to you, that's a perfectly good reason to listen to it. It doesn't need the mythology.
How to test it on yourself
You can run a simple blind test with a friend in about ten minutes. It isn't a scientific trial, just a way to find out what your own ears think.
Pick a song you know well and get it in both tunings. Many tracks are posted in both, or a pitch-shifting app can lower a 440 Hz recording to 432 Hz.
Have your friend play the two versions in random order without telling you which is which. Headphones help you hear the detail.
Rate each one from one to ten on how much you like it.
Repeat with a few different songs.
If you keep picking the 432 Hz version without knowing which it is, you've learned something about your own ears. If your scores look like a coin toss, that's useful to know too.
Where Sound Orbit fits
Sound Orbit is built around binaural beats and isochronic tones rather than a tuning standard. The Mixer includes all nine Solfeggio tones as layers you can stack with nature sounds, harmonic layers and a brainwave band, and the Solfeggio layers don't require Premium. Binaural beats need headphones; Solfeggio tones and isochronic tones work on speakers too.
Download for iOS · Download for Android
Sound Orbit is a sound-wellness app, not a medical device. Nothing here is medical advice. If you're dealing with persistent anxiety, poor sleep, or pain, talk to someone qualified.
Sources referenced
International Organization for Standardization. ISO 16:1975, Acoustics: Standard tuning frequency (standard musical pitch). First issued as ISO Recommendation R 16, 1955.
A440 (pitch standard). Wikipedia, accessed November 9, 2026 (1834 Stuttgart recommendation, 1939 London conference, French 435 Hz standard, orchestras at 440–444 Hz).
Scientific pitch. Wikipedia, accessed November 9, 2026 (C = 256 Hz, A ≈ 430.54 Hz; Verdi and 432 Hz; Schiller Institute campaign).
Verdi, G. Letter of February 10, 1884, to the Italian government's commission on pitch.
Carioli, A. (2026, July 30). Perché si dice "dare il La"? Tra le proteste di Verdi e la bufala del complotto nazista. Focus.it (the Goebbels claim).
Calamassi, D., & Pomponi, G. P. (2019). Music tuned to 440 Hz versus 432 Hz and the health effects: a double-blind cross-over pilot study. Explore (NY), 15(4), 283–290. PMID 31031095. Corrigendum: Explore (NY), 16(1), 8 (2020), PMID 32113613.
Calamassi, D., Lucicesare, A., Pomponi, G. P., & Bambi, S. (2020). Music tuned to 432 Hz versus music tuned to 440 Hz for improving sleep in patients with spinal cord injuries: a double-blind cross-over pilot study. Acta Biomedica, 91(12-S), e2020008. PMID 33263352.
Aravena, P. C., Almonacid, C., & Mancilla, M. I. (2020). Effect of music at 432 Hz and 440 Hz on dental anxiety and salivary cortisol levels in patients undergoing tooth extraction: a randomized clinical trial. Journal of Applied Oral Science, 28, e20190601. PMID 32401941.
Calamassi, D., Li Vigni, M. L., Fumagalli, C., Gheri, F., Pomponi, G. P., & Bambi, S. (2022). The listening to music tuned to 440 Hz versus 432 Hz to reduce anxiety and stress in emergency nurses during the COVID-19 pandemic: a double-blind, randomized controlled pilot study. Acta Biomedica, 93(S2), e2022149. PMID 35545982.
Hohneck, A., Rodríguez, Á. M., Weingärtner, S., et al. (2025). Differential effects of sound interventions tuned to 432 Hz or 443 Hz on cardiovascular parameters in cancer patients: a randomized cross-over trial. BMC Complementary Medicine and Therapies, 25(1), 18. PMID 39844155.
Jebabli, N., et al. (2025). Effects of 440-Hz vs. 432-Hz preferred music frequencies, during warm-up, on intermittent anaerobic speed test performance in men and women kickboxers: a double-blind crossover study. PeerJ, 13, e19084. PMID 40061232.
Jebabli, N., et al. (2025). Effect of listening to preferred music at different frequencies during warmup on physical performance and psychophysiological responses in male athletes. Scientific Reports, 15. PMID 41093978.
Bozok, Ü. G., Böyük Özcan, G., Bayraktar, B., & Özen, D. (2026). Acute music-frequency exposure modulates salivary stress and neurotrophic markers in young adults: a randomized controlled trial. Brain and Behavior. PMID 42043979.
Solmization. Encyclopaedia Britannica (Guido of Arezzo, "Ut queant laxis").
Gold, S. (2025, February 26). What are Solfeggio frequencies: is there science behind these sacred sounds? Discovery UK (Puleo, mid-1970s; six to nine tones).
Good, C. (2015, July 7). Solfeggio frequencies. Skeptoid, episode 474 (no evidence that tones repair DNA).
Horowitz, L. G. (1999). Healing Codes for the Biological Apocalypse. Tetrahedron Publishing Group.
