About CelloTuner.io
How the pitch meter, frequency references, privacy model, safety limits, and correction process work.
Purpose and Scope
CelloTuner.io is a cello-specific pitch tool and reference library. It covers standard C2–G2–D3–A3 tuning, several documented alternate tunings, open-string frequencies, a safety-conscious tuning sequence, and common problems such as slipping pegs, maxed fine tuners, unstable readings, and a leaning bridge. The goal is to help a player make an informed adjustment, not simply show a green meter.
What the Tuner Measures
After you grant microphone access, the tuner estimates the strongest repeating frequency in the sound. It compares that estimate with the selected cello string and reports the difference in cents. Pitch estimation uses an autocorrelation-based detector in the browser. The tuner processes microphone samples on the device; it does not upload or intentionally store the audio.
Frequency Method
Standard A440 targets use 12-tone equal temperament: frequency equals 440 × 2(n − 69) / 12, where n is the MIDI note number. That produces C2 = 65.41 Hz, G2 = 98.00 Hz, D3 = 146.83 Hz, and A3 = 220.00 Hz. The frequency calculator applies the same formula to A4 references from 415 through 445 Hz.
These are tuning targets, not a promise that a bowed acoustic string will remain at one fixed decimal value. Bow pressure, vibrato, temperature, room noise, harmonics, string condition, and instrument response all move the reading.
Limits and Instrument Safety
A microphone can measure a repeating sound, but it cannot inspect a bridge, peg, string winding, seam, tailpiece, or fingerboard. It also cannot tell whether a beginner is tightening toward the wrong octave. The guides therefore separate measurement problems from mechanical problems and say when to stop. If hardware binds, the bridge is visibly leaning, or the octave is uncertain, a teacher or repair professional should inspect the instrument before more tension is added.
Ownership, Review, and Corrections
John Sorrentino created and maintains CelloTuner.io as part of a collection of focused browser tools. Tuning references are reviewed when the detector, preset library, or educational pages change. The site is independent and is not a substitute for instruction from a cellist, teacher, ensemble director, string maker, or luthier.
If a note, octave, frequency, tuning name, or instruction appears incorrect, use the contact page and include the page, device, browser, selected tuning, and the result you expected. Reproducible corrections take priority over adding more presets.