Reference guide · 4 min
One pitch, three languages
Musicians name pitches, synthesizers count MIDI notes, and analyzers measure hertz. This converter keeps the three views locked together under an adjustable A4 reference so a value from any source becomes usable everywhere.
Quick start
A reliable starting point
- 01Confirm the reference
Most modern material uses A4 = 440 Hz. Change the reference only if the session or ensemble is tuned differently.
- 02Enter what you know
Pick a note and octave, type a frequency, or type a MIDI number. The other representations update immediately.
- 03Read the cents offset
A measured frequency rarely lands exactly on a note. The offset shows how far the value sits from the nearest equal-tempered pitch.
The math
01Equal temperament in one line
Equal temperament divides every octave into twelve identical ratios. Each semitone multiplies frequency by the twelfth root of two, and every octave doubles it.
MIDI numbers simply count those semitones: A4 is note 69, middle C is note 60, and the full range runs from 0 (C-1, about 8.2 Hz) to 127 (G9, above 12.5 kHz).
f = A4 × 2^((n − 69) ÷ 12)Tuning standards
02Why A4 is adjustable
- 440 Hz: the modern default for recorded and electronic music.
- 441–443 Hz: common orchestral choices for a slightly brighter ensemble sound.
- 432 Hz: a popular alternative reference; the math is identical, only the anchor moves.
- 415 Hz: a frequent baroque pitch, roughly a semitone below modern tuning.
Octave conventions
03Middle C is not always called C4
This tool follows the scientific convention where middle C (MIDI 60) is C4. Some DAWs and manufacturers label the same note C3 or C5, so an octave disagreement between programs is a naming difference, not a pitch difference.
When exchanging notes between environments, trust the MIDI number or the frequency—they are unambiguous.
Studio uses
04Where the numbers help a mix
- Tune kicks and 808s: find the fundamental of your key's tonic and match the sample to it.
- Surgical EQ: convert a resonant note to hertz before cutting or boosting.
- Sound design: set oscillators, filters, and resonators by exact frequency instead of sweeping blindly.
- Sub decisions: pitches below roughly E1 (41 Hz) live mostly in the subwoofer—arrange bass lines accordingly.
Keep in mind
Studio notes
One cent is a hundredth of a semitone; offsets under about five cents are rarely audible in context.
EQ decisions aim at the fundamental, but timbre lives in the harmonics—sweep above the root too.
If an instrument reads consistently sharp or flat, verify the A4 reference before retuning everything.