What a chromatic tuner does that a string tuner does not
A string-specific tuner assumes you are tuning one of a few known notes, so it asks for the instrument first. A chromatic tuner makes no such assumption. It hears a pitch, finds the closest of the twelve semitones in any octave, and tells you how far off you are. That one idea covers a violin, a trumpet, a mandolin, a flute, a hand-built banjo, a recorder or your own voice, which is why it is the general-purpose option when a ready-made list does not exist.
The display has three readings. The big letter is the nearest note name, with its octave number, like A4 or F#3. The needle shows the distance from that note in cents. Beneath them sits the target frequency in hertz, which is the exact pitch of the note you are being compared with at the current reference. When the pitch is within a few cents of the target, the needle sits at the center and you are in tune.
Because the tuner does not know what you intend to play, it cannot tell you which note you should aim for. If you are aiming for E and the display says F, you are a semitone sharp from your target and you should lower the pitch. It is your job to know the note you want, and the tuner's job to show the pitch you have.
Cents, and the math behind the needle
Western music divides each octave into twelve equal semitones, and each semitone into one hundred cents. An octave is therefore 1,200 cents. Because every semitone is the same frequency ratio, about 1.0595, a cent is a ratio of 2 to the power of 1/1200, around 0.058 percent. At A4 that is 0.25 Hz. At A2 the same cent is only 0.06 Hz.
This is why a cents readout is more useful than hertz. If you are 2 Hz flat on a low string, you may be a long way out of tune. If you are 2 Hz flat on a high note, you are barely off. The formula behind the needle is the same for every pitch: cents equals 1,200 times the base 2 logarithm of the heard frequency divided by the target.
Many people notice a difference of roughly five to ten cents when two notes sound together, and trained ears can hear a few cents in a sustained tone. Beating, the slow wobble you hear when two near-identical pitches interfere, gets slower as you move closer to unison. Tuners help you reach the smooth zone where the wobble disappears.
Real instruments are not perfectly steady. A violin with vibrato swings several cents either side of its center, and a voice drifts. Aim to hold a plain note without vibrato for a second so the display can average.
Choosing the A4 reference: 415, 432, 440, 442
Every note on the display is calculated from a single reference, the frequency assigned to the A above middle C. The A4 box accepts 415 to 466 Hz, and chips are provided for 415, 432, 440, 442 and 443. The table in the Numbers tab shows what changing it does to C4 and E4 and how far each setting sits from 440.
The modern default is 440 Hz. Many European and some American orchestras tune slightly higher, 442 or 443, often for a brighter sound. If you play along with a group that tunes this way, set the same value, otherwise you will be a consistently flat player who is perfectly in tune with yourself.
415 Hz is the common pitch for baroque ensembles playing period instruments, almost exactly a semitone below 440, at 415.3. Harpsichords and gut-strung instruments are often set to it. 432 Hz is a popular preference among some musicians who like a slightly softer sound. It is a choice of taste, a bit under a third of a semitone below 440, and no more correct than the others. Use whichever matches the people and the keyboard you are playing with.
A piano or an electronic keyboard cannot easily move its pitch, so when you play with one, set the tuner to match the keyboard. Many digital pianos let you change their A4 setting in small steps; check the manual.
Transposing instruments and the written note
Some instruments sound a different pitch from the note they read. A B-flat trumpet or clarinet, when it plays a written C, produces a B-flat, a whole step lower. An E-flat alto saxophone produces an E-flat when a C is written, which is a major sixth lower. A horn in F sounds a perfect fifth below the written note. These conventions exist so that players of the same family can use the same fingerings across different sizes of instrument.
The instrument setting handles this. Choose concert C, B-flat, E-flat or F, and the display shows the written note for the instrument you choose. A trumpet player sounding a concert B-flat sees a written C, so the name matches the music in front of them. The needle and the cents are unchanged, because the pitch itself is the same; only the label moves.
Many bands tune to a concert B-flat, and a section leader will ask for an A or a concert F. If the conductor asks for a concert note, you need to know which written note it corresponds to on your instrument. Setting the instrument key removes the mental arithmetic, and you tune the written note that matches the one on the page.
Banjo, mandolin, violin and other strings
People often ask if a guitar tuner is enough for another stringed instrument. The answer is that a chromatic tuner is what you want, since their open strings differ. A mandolin is tuned in fifths, G D A E, like a violin. An open-G five-string banjo is typically g D G B D, with a short fifth string higher than the rest. A violin is also tuned G D A E, and a cello runs C G D A, an octave and a fifth lower.
With the chromatic tuner you pluck each string and read the note name. On a violin, pluck the A string, and if the display shows A4 with the needle centered, move on to the next string. Violin and mandolin strings are close to the instrument's top range, and the pitch is steady and easy to read. Bowed notes work well too, as long as you keep the bow smooth.
A banjo has a bright, sharp attack that gives a clear reading but dies quickly. Pluck and watch the first half second. For a violin, avoid pressing on the string with your finger so the open string rings undisturbed. For a mandolin, which has paired strings, pluck one string of the pair at a time and mute the other with a finger, or the beating between two slightly different pitches will blur the display.
Wind instruments are trickier, since the pitch changes with the air temperature and your embouchure. Warm up the instrument first, because a cold flute is flat. Play a long note, listen for the display to settle and make small adjustments to the length of the instrument.
Singing, humming and reading the display
The tuner is useful for voices too. Sing a sustained vowel and see where it lands. Vocal pitch moves around a lot more than an instrument's, so look for the average. Singers can use the display to practice hitting a note without drifting flat at the end of a phrase, which is a common habit.
If the display jumps between two names, you are probably sitting on the border, about 50 cents from each of them. If it jumps by an octave, the detector may have latched onto an overtone. Let the note ring, move closer to the microphone, or play in a quieter space. Low pitches below roughly 60 Hz are hard for small phone microphones, so a double bass or a bass guitar may read more reliably on a harmonic.
Detection follows a YIN-style method, which looks for the repeating period of the waveform. It prefers a single clear tone. Chords, which contain several pitches at once, confuse it; the chord finder on this site is the right tool for naming a chord.
Privacy of the microphone
As an online tuner it needs no install, and pitch is worked out while you play. The sound is not recorded and never leaves the browser, and the microphone stops when you close the tab. The reference and the instrument key reset to 440 Hz and concert pitch each time you open the page.
Frequently asked questions
What is a chromatic tuner?
A chromatic tuner detects any pitch and names the nearest of the twelve semitones, instead of comparing against a fixed list of strings. It also reports how many cents sharp or flat you are. Because it needs no preset, it works for violins, wind instruments, banjos, voices and anything else that makes a steady tone.
What is a chromatic tuner used for?
It is used to tune instruments that are not covered by a dedicated string list, to check intonation on wind instruments, to set a violin or mandolin, and to practice singing in pitch. Players also use it to find out which note an unknown sound is, and to match a keyboard pitch.
Can you tune a banjo with a guitar tuner?
You can if the tuner is chromatic, since you can pluck each banjo string and read its note against the open-G list: g, D, G, B, D. A guitar tuner that only offers guitar strings will name the wrong target. Mute the short fifth string when you check the others.
Can you tune a mandolin with a guitar tuner?
Yes, as long as the tuner can read any note. A mandolin is tuned G D A E, which a chromatic tuner shows directly. Each course has two strings, so pluck them one at a time while you press a finger lightly on the other to stop the pair from blurring the needle.
Which A4 reference should I choose?
Use 440 Hz unless you are playing with something else. Choose 442 or 443 for orchestras that tune higher, 415 for baroque ensembles, and 432 if you simply prefer a slightly lower sound. What matters most is that everyone you play with uses the same reference.
How do I tune a B-flat trumpet or clarinet?
Set the instrument to B-flat. The display then shows the written note, so a concert B-flat appears as a C. Play a long, steady note, adjust the tuning slide or barrel until the needle centers, and check a few other notes, since instruments are rarely equally in tune everywhere.