What is A3 vs A4 vs A5?

Octaves — factor of 2 each. At 440: A3=220, A4=440 (standard), A5=880. 4 refers to piano-notation octave with middle C. A4 is 9 semitones above middle C (C4). Octave selector hears same note at 3 different pitches.

What does cents readout show?

Logarithmic pitch — 100 cents = semitone, 1200 = octave. Shows offset from A440. 440=0¢, 432=−31.77¢ (flat), 443=+11.76¢ (sharp), 444=+15.67¢. Note change shifts to that note's cents — same offset under given tuning.

Tune instrument with this?

Yes for general acoustic tuning. Audio driver pitch errors limit precision. For sub-cent accuracy use dedicated chromatic tuner. For Baroque A415 use general Tone Generator under Wave Generators.

Which waveform for tuning?

Sine best for tuning — no harmonics, pure fundamental, ear matches directly. Triangle has soft harmonics. Square has rich odd harmonics (synth sound). Sawtooth has all harmonics (bowed-string). Harmonic-rich can confuse pitch-matching — ear locks onto harmonic instead of fundamental. Stick with sine.

16-bit mono WAV at 44.1 kHz with current note + waveform, chosen duration (10/30/60 sec). 50ms fade-in/out to avoid clicks. Filename includes tuning + note + duration (440Hz-A4-10s.wav).

Avoid sustained loud pure tones — pure sines piercing, contribute to hearing fatigue. Moderate volume. Tinnitus/hearing sensitivity: lowest audible volume. Avoid if seizure disorder; consult doctor about pure-tone exposure.

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440 Hz Tone Generator A4 concert pitch reference

Pure A440 reference tone — the international concert-pitch standard formalized by ISO 16 in 1955. Compare against alternative tunings (432 Hz "natural", 443 Hz some European orchestras, 444 Hz some choirs). Full 12-note chromatic reference chart, four waveforms, octave selector A3/A4/A5, cents-vs-440 readout, session timer, 10/30/60-second WAV export.

⚠ The value of A440 is mostly that it's a common reference — not that 440 Hz itself has special acoustic or biological properties. Pitch standardization makes it possible to play together, manufacture interchangeable instruments, and synchronize recordings. Use this tool for tuning instruments to ISO standard or for A/B comparing standard vs alternative tunings.

A4 tuning

Octave

Waveform

12-note reference chart

Frequencies update live when you switch tuning or octave. Click any note to play it.

WAV export

Renders the current note + waveform as a 16-bit mono WAV at 44.1 kHz.

Master

Volume 30 %

Moderate volume — pure sines can sound piercing at high levels.

Idle — press Play.

Session timer

Time remaining

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Audio fades over the configured fade-out at session end.

Fade in / fade out

Fade duration 3 s

Short by default — tuning references want quick on/off.

Live readouts

Current note

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Cents vs 440 std

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Sample rate

—

Audio output waveform (live)

A440 Concert Pitch — What and How

A440 is the international concert-pitch standard. Standardized by ISO 16 in 1955 (and earlier through industry agreements going back to the late 19th century), it specifies that the A above middle C — known as A4 in modern notation — should equal 440 Hz. Orchestras, music software, instrument tuners, and recording studios worldwide use 440 Hz as the common reference.

The value of 440 is mostly that it's standard. There's nothing acoustically or biologically special about 440 Hz; the standardization itself is the win. Before standardization, "concert pitch" varied wildly across cities, countries, and historical eras — Baroque pitch was often around 415 Hz, French opera in the 19th century used pitches as high as 456 Hz, and individual orchestras and choirs each had their own conventions. Common reference makes it possible to play together, manufacture interchangeable instruments, and tune across recordings.

Common alternative tunings (included as A/B options)

432 Hz — popular "natural tuning" in alternative-music and meditation circles; some musicians prefer its slightly warmer character. About 31.77 cents flat of 440.
440 Hz — the ISO standard (default).
443 Hz — used by some European orchestras (Berlin Philharmonic among others have used pitches in this range historically; modern usage varies). About 11.76 cents sharp of 440.
444 Hz — used by some choirs and a small number of orchestras seeking a slightly brighter character. About 15.67 cents sharp of 440.

Historical tunings not in this tool (use the Tone Generator under Wave Generators for arbitrary frequencies): 415 Hz Baroque/Historically Informed Performance tuning, 392 Hz French Baroque, 466 Hz 17th-century Venetian.

How the 12-note chart works

The chart shows all 12 chromatic notes (C, C#, D, D#, E, F, F#, G, G#, A, A#, B) under the chosen A4 tuning, calculated as 12-tone equal temperament — each adjacent semitone is a factor of 2^(1/12). Switching the A4 base shifts every note proportionally. Click any note button to play that specific frequency.

Using this tool for instrument tuning

Pick A4 = 440 Hz tuning, select the A4 octave, and click the A note. Tune your instrument against this reference. For sub-cent accuracy use a dedicated chromatic tuner; for general acoustic-instrument tuning, this is well within usable accuracy. For Baroque or Historically Informed Performance, the 432 Hz option is the closest match in this tool to common historical tunings (though 415 Hz is more historically accurate for Baroque — use the general Tone Generator for that).

Frequently Asked Questions

Why is 440 Hz the standard?

Practical convenience. It sits in the middle of the range various 19th and early 20th century industry pitch standards converged toward. The ISO 16 standardization in 1955 was an agreement among instrument makers, broadcasters, and music industry bodies — they needed a common reference to make instruments interchangeable and broadcasts consistent. 440 Hz won mostly because it was already widely used in industry by then. It's not a magic number; it's a useful convention.

Was 440 Hz introduced for malicious reasons?

No. This is a conspiracy theory that surfaces in alternative-medicine and esoteric circles. The historical record shows 440 Hz being discussed and adopted incrementally through the late 19th and early 20th centuries by music industry bodies seeking standardization. There is no documented effort to use 440 Hz for population manipulation. The standardization process is well-documented and openly conducted; the conspiracy framing conflates standardization with nefarious intent.

What about 432 Hz being "more natural"?

The audible difference between 440 and 432 is real (about 31.77 cents, between a quarter tone and a semitone). Some musicians genuinely prefer 432 Hz for its slightly warmer character. The claim that 432 Hz has special biological-resonance properties — that it harmonizes with the Earth, repairs DNA, or aligns with the heart chakra — is not supported by peer-reviewed evidence. If you prefer the sound of 432, use 432; if you prefer 440, use 440. Don't pick based on pseudoscience.

Why do some orchestras use 443 or 444?

A slightly higher A4 gives instruments a slightly brighter, more brilliant character — some orchestras and conductors prefer this sound, especially for certain repertoire. The Berlin Philharmonic has used pitches in the 443–445 Hz range at various points; some Eastern European orchestras tune higher than 440. It's an artistic preference balanced against the practical inconvenience of being "out of standard" — instruments must be tunable to the higher pitch and players must adjust. Choirs sometimes tune higher (444+) for similar brilliance, though this can strain singers' voices.

What's the difference between A3, A4, A5?

Octaves — each one is a factor of 2 in frequency. At 440 Hz tuning: A3 = 220 Hz (one octave below A4), A4 = 440 Hz (standard concert pitch), A5 = 880 Hz (one octave above). The "4" in A4 refers to the octave where middle C lives in standard piano notation; A4 is 9 semitones above middle C (C4). The octave selector in this tool lets you hear the same note at three different pitches.

What does the cents readout show?

Cents are a logarithmic pitch unit — 100 cents = one semitone, 1200 cents = one octave. The readout shows the offset from standard A440. On 440 Hz tuning: 0¢. On 432 Hz: −31.77¢ (flat). On 443 Hz: +11.76¢ (sharp). On 444 Hz: +15.67¢. Selecting a different note shifts the readout to that note's cents-vs-440 value (which is the same offset since all notes shift together under a given tuning).

Can I tune my instrument with this?

Yes, for general acoustic-instrument tuning. The accuracy depends on the audio output path (audio drivers can introduce slight pitch errors), but for most instruments this is well within usable accuracy. For precision tuning (e.g. orchestral instruments needing <1 cent accuracy), use a dedicated chromatic tuner. For Baroque tuning (A415), use the general Tone Generator under Wave Generators which lets you enter any frequency.

Which waveform should I use for tuning?

Sine (default) is the best choice for tuning — no harmonics, just the pure fundamental frequency, so your ear can match the pitch directly. Triangle has soft harmonics. Square has rich odd harmonics (a "synth" sound). Sawtooth has all harmonics (closer to bowed strings). The harmonic-rich waveforms (square/sawtooth) can confuse pitch-matching because your ear may lock onto a harmonic instead of the fundamental. For tuning, stick with sine.

What does the WAV export include?

A 16-bit mono WAV file at 44.1 kHz sample rate containing the currently selected note + waveform, rendered for the chosen duration (10, 30, or 60 seconds). Includes a 50ms fade-in and 50ms fade-out to avoid clicks. The filename includes the tuning, note, and duration (e.g. 440Hz-A4-10s.wav).

Safety reminders?

Avoid sustained loud pure tones — pure sines can sound piercing and contribute to hearing fatigue. Keep volume moderate. If you have tinnitus or hearing sensitivity, use the lowest volume that lets you clearly hear the tone. Avoid if you have a seizure disorder; consult your doctor about any pure-tone exposure.

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