Bass Won't Tune? How to Tune Low Strings Accurately

How low a bass really is

Standard tuning on a four-string bass, from the thickest string, is E1, A1, D2, G2. With the reference set to A4 = 440 Hz, that works out to:

• 4th string, E1: about 41.2 Hz
• 3rd string, A1: 55 Hz
• 2nd string, D2: about 73.4 Hz
• 1st string, G2: about 98.0 Hz

Your low E is exactly one octave below a guitar’s low E (E2, about 82.4 Hz). While the guitar string vibrates 82 times a second, the bass string vibrates 41 times. Tune down a half step and the low string drops to E♭1, about 38.9 Hz, which is even harder for a small microphone to hear.

Why phone mics struggle with low notes

The tiny microphones used in phones (MEMS microphones) are often designed to lose sensitivity at very low frequencies. Microphone maker documentation describes a roll-off below a cutoff frequency, and that cutoff varies by design, from a few tens of hertz up to around 100 Hz. Phone makers rarely publish which microphone they use, so the same bass can read cleanly on one phone and poorly on another.

When the microphone hears less of the fundamental (the 41 Hz part of the note), the overtones above it become relatively louder. That’s when a tuner may briefly read the note an octave high, or the needle wanders instead of settling.

Our bass tuner analyzes the sound about 20 times per second and displays the median of the last few readings, so a single wild reading doesn’t throw the needle around. If what it hears is more than 50 cents away from the target string, it also shows the note it’s actually hearing, such as “Hearing E2,” so you can spot an octave error immediately.

How and where to pluck

The way you pluck makes a bigger difference than most people expect.

• Pluck gently, once. A hard attack is noisy and full of overtones for the first moment, which makes the reading jumpy. Pluck softly with your finger and watch the needle while the note sustains evenly.
• Pluck closer to the neck. Plucking near the bridge emphasizes the upper harmonics and makes the tone bright. Plucking closer to the middle of the string, near the end of the fingerboard, reduces those upper harmonics, so the fundamental and lower partials make up more of the sound. That’s easier for a tuner to read.
• Mute the other strings. Sympathetic ringing from neighboring strings confuses the tuner. Rest your palm lightly on the strings you’re not tuning.
• Get the mic close. Hold the phone near the amp or the body of the bass, and move somewhere quiet if the room is noisy.

Lock the tuner to one string

The bass tuner automatically picks the string closest to what it hears. If a string is way out of tune, it can guess the wrong one. Tap the string name on screen to lock the tuner to that string. It also plays that string’s reference pitch, so you can get close by ear first and finish with the needle. Tap the same name again to return to automatic mode.

Tuning with 12th-fret harmonics

To play a harmonic, rest a fingertip lightly on the string directly above the 12th fret without pressing it down, pluck, and lift your finger. The 12th fret sits exactly halfway along the string, so the fundamental disappears and you hear a clean tone one octave above the open string. On the 4th string you get E2 instead of E1.

That higher note is easier for a phone mic to pick up, and it has fewer messy overtones, so the tuner often locks on faster. There’s one catch: the bass tuner only looks for E1, A1, D2 and G2, so an E2 harmonic may be matched to the wrong string. When you tune with harmonics, open the main tuner page, choose Chromatic (any note), and tune each string’s harmonic to the octave above: E2, A2, D3 and G3.

Clip-on tuners and direct input

If your phone just won’t cooperate, skip the air altogether:

• Clip-on tuner. Clipped to the headstock, it reads the vibration traveling through the instrument rather than sound in the room, so background noise bothers it much less. Handy in a loud rehearsal room.
• Direct input. Plug the bass into a tuner pedal or an audio interface and the tuner reads the signal straight from the pickups, with no microphone involved.

A phone tuner wins on convenience: it’s always in your pocket. In a quiet room, with a gentle pluck and the help of string locking or harmonics, it can handle a low E1 in many cases. Some phone mics may still struggle, and that’s when a clip-on or a cable is worth reaching for. After all four strings are in tune, make a habit of going around once more to double-check.