Play reference tones for musical notes using Web Audio API with tuning standard adjustment (A4 = 440Hz).
Most things labeled 'tuner' listen to you; this one plays for you. Pick a note and it sounds that pitch as a steady reference tone, so you can match an instrument or voice by ear. Every frequency comes from the equal-tempered scale anchored to one number, the A4 tuning standard (440 Hz by default); raise or lower that anchor and every note rescales by the same ratio. The easy surprise is the octave: A3, A4, and A5 sound 220, 440, and 880 Hz, doubling at each octave, so reading the octave number on the note you select is half the battle.
A concrete input and expected output from the current implementation.
Input
Select note E4 (the guitar's first string) with the tuning standard left at A4 = 440 Hz.
Expected output
A steady reference tone at 329.63 Hz.
E4 is five semitones below A4, and each equal-tempered semitone is a factor of 2^(1/12), about 1.0595, so the pitch is 440 / 2^(5/12) = 329.63 Hz. Raise the standard to 442 Hz and the same note sounds 331.13 Hz, because every note scales by the ratio 442/440.
The page computes every note from the formula f = 440 * 2^((n-69)/12), where n is the MIDI note number of the selected pitch and 440 is the A4 standard. An octave doubles the frequency: A4 = 440 Hz, A5 = 880 Hz, A3 = 220 Hz. Each of the twelve semitones in between multiplies the frequency by 2^(1/12), about 1.0595. The tone is generated locally in the browser via the Web Audio API.
Choosing A4 = 442 Hz multiplies every note by 442/440 = 1.0045, about 7.85 cents sharper, a pitch many orchestras tune to; choosing 415 Hz, the baroque pitch, multiplies by 415/440 = 0.9432, about 101 cents, just over a semitone flatter than 440. The multiplier is uniform, so A2 moves by the same proportion as A6 even though the hertz change differs (0.5 Hz versus 8 Hz at 442).
The reference here is mathematically exact for the equal-tempered scale at the standard you selected. If the instrument tunes to a different standard (many orchestras use 442 Hz) it will sit about 7.85 cents sharper than a 440 reference. Pianos also use stretch tuning in the outer octaves, and tuner apps may default to another standard. A small systematic offset is expected; a large one is usually a wrong octave.
Yes. Standard tuning at A4 = 440 is E2, A2, D3, G3, B3, and E4, sounding 82.41, 110.00, 146.83, 196.00, 246.94, and 329.63 Hz. Play each string's note here and adjust the peg until your string matches. As you get close you will hear a slow wavering called beating that disappears at exactly the same frequency. What the tool will not do is tell you which way to turn the peg.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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