Why your tuner jumps around, and how to get a steady reading

Short answer: a tuner needs one clean, ringing note. Most jumping needles come from the first moment of the pluck, other strings ringing, or a microphone that can barely hear the note.

Wait for the attack to pass

A plucked string starts sharp. For the first moment after you hit it, the string is stretched further than it will be once it settles, so the pitch is a little high. It then drops by a few cents and steadies. If you read the needle right at the attack, you tune slightly flat.

Pluck at a normal strength and watch the needle after it settles, not during the first half second. A very hard pluck makes the effect bigger.

Only one note at a time

A chromatic tuner looks for one repeating pattern. Two strings ringing together make a pattern that keeps changing, and the needle follows that. Guitar and bass strings also ring along with each other without being touched, so:

• Rest your other hand lightly across the strings you are not tuning.
• Stop the last string before you play the next one.
• Don't strum to check the tuning until each string reads right on its own.

If it shows the wrong note or octave

A string's sound contains its fundamental plus a stack of overtones. On low notes, small microphones hear the overtones far better than the fundamental. A tuner may then read an A2 string as A3, or a note a fifth up, because that overtone is what it hears loudest.

Pluck nearer the middle of the string, which brings out the fundamental. Move the microphone closer. If the tuner has instrument presets, use them: it will then match the nearest string instead of naming any note it hears. In TuneLog and in our online tuner, choosing your instrument does this.

Low strings on a phone

Phone and laptop microphones are built for voices, and they roll off low frequencies. The low E of a bass is 41 Hz and the low B of a 5-string is 31 Hz, well below most speech. There are a few fixes:

• Hold the phone close to the instrument, near the bridge or the sound hole.
• With an electric bass or guitar, put the phone near the speaker of your amp.
• Tune a harmonic instead. The 12th-fret harmonic is the same note one octave up, which is far easier to hear. Read it as the same note name, one octave higher.

A noisy room

Fans, a fridge or other players add sound that the tuner has to ignore. A tuner does best when the note is much louder than the room, so get closer rather than playing harder. If the room is too loud, use a contact tuner or a direct cable if you have one.

Some phone apps and browser pages also run the microphone through voice processing. That is good for calls, but it can treat a steady note as noise and fade it out. TuneLog asks for the unprocessed signal where the phone offers it, and our online tuner asks the browser to turn that processing off.

It was in tune a minute ago

• New strings stretch. They keep going flat for a while. Pull each one gently away from the fretboard, retune and repeat until it holds.
• Tune up to the note. If a string is sharp, go below the note first, then come up. Slack around the tuning post can otherwise let it slip flat as you play.
• Temperature matters. An instrument brought in from the cold will drift as it warms up. Give it a few minutes before tuning for good.

How close is close enough?

A cent is a hundredth of a semitone. TuneLog marks 5 cents either side as the in-tune zone and ticks a string off once it stays within 3 cents. Trying to hold a needle exactly on zero is usually wasted effort, because a ringing string itself drifts by a few cents as it fades.

If each string reads right but chords still sound a bit off, the tuner may not be at fault. Guitar frets are a compromise, and an instrument's intonation also depends on its setup. A shop can check that.