Bass Tuning Chart: 4, 5 & 6-String Frequencies

The electric bass guitar carries the rhythmic and harmonic foundation of most modern ensembles. Its open strings sound one octave below the lowest four strings of a standard guitar: E1 to G2 on a four-string, with a low B0 = 30.87 Hz added on a five-string and a high C3 on a six-string.

The fundamental frequency of any note in 12-tone equal temperament referenced to A4 = 440 Hz is:

f = 440 × 2^((m − 69)/12)

where m is the MIDI number (E1 = 28, A1 = 33). The charts below give exact frequencies, MIDI values, periods in milliseconds and the practical limits of detecting these notes.

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1. Standard 4-String Bass (E1–A1–D2–G2)

Standard four-string tuning ascends in perfect fourths (5 semitones, 500 cents), matching the lower four guitar strings transposed down an octave.

String	Note	Frequency (Hz)	MIDI	Period (ms)
4 (lowest)	E1	41.20	28	24.27
3	A1	55.00	33	18.18
2	D2	73.42	38	13.62
1 (highest)	G2	98.00	43	10.20

The period column is the time for one complete cycle. It matters for tuning: the lower the note, the longer a detector must listen to measure a full cycle.

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2. 5-String Bass with Low B (B0–E1–A1–D2–G2)

The five-string adds a thick low B below the E1, reaching into the sub-bass register.

String	Note	Frequency (Hz)	MIDI	Period (ms)
5 (lowest)	B0	30.87	23	32.40
4	E1	41.20	28	24.27
3	A1	55.00	33	18.18
2	D2	73.42	38	13.62
1 (highest)	G2	98.00	43	10.20

What you actually hear on a low B

A B0 string completes one cycle every 32.40 ms. Compact cabinets and small practice amps cannot move enough air to reproduce that fundamental, so what reaches your ears is mostly the harmonic series above it: 2nd harmonic B1 = 61.74 Hz, 3rd harmonic F#2 = 92.60 Hz, 4th harmonic B2 = 123.47 Hz. The ear reconstructs the missing fundamental from those harmonics, which is why a bass line still sounds like a low B on a system that cannot move air at 30.87 Hz. The same physics causes the classic tuning error: a detector hearing only harmonics can lock onto the 2nd harmonic and report E2 = 82.41 Hz for a string sitting at E1 = 41.20 Hz.

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3. 6-String Bass Reference (B0–E1–A1–D2–G2–C3)

A six-string keeps the low B and adds a high C3 a perfect fourth above G2.

String	Note	Frequency (Hz)	MIDI	Function
6 (lowest)	B0	30.87	23	Sub-bass extension
5	E1	41.20	28	Standard root
4	A1	55.00	33	Standard
3	D2	73.42	38	Standard
2	G2	98.00	43	Standard top
1 (highest)	C3	130.81	48	Melodic register

Our tuner ships four- and five-string presets; the six-string row is a reference.

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4. Drop Tunings (Drop D, Drop C and Drop A)

Drop tunings lower the lowest string so power chords and octave riffs line up with guitar parts.

Tuning	String 4	String 3	String 2	String 1
Drop D	D1 36.71 Hz	A1 55.00 Hz	D2 73.42 Hz	G2 98.00 Hz
Drop C	C1 32.70 Hz	G1 49.00 Hz	C2 65.41 Hz	F2 87.31 Hz

Drop D lowers only the 4th string, by 2 semitones (−200 cents) from E1 = 41.20 Hz to D1 = 36.71 Hz. Drop C lowers the whole instrument one whole step and drops the 4th string a further whole step to C1 = 32.70 Hz. A five-string can go further with drop A (A0 = 27.50 Hz, one cycle every 36.36 ms), which is at the edge of what most bass rigs reproduce.

The bass tuner’s presets are standard four- and five-string, so for a dropped low string the practical routes are the Chromatic Tuner, which reads D1 or C1 directly, or the Drop D Tuner, whose D2 = 73.42 Hz target matches the 12th-fret harmonic of a bass string dropped to D1.

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5. Why Low Bass Detection Needs Decimation

Detecting a 30.87 Hz fundamental with a microphone is a length problem. One cycle of B0 lasts 32.40 ms; at a 44.1 kHz sample rate that is 1,429 samples. A standard 1,024-sample analysis frame covers only 23.2 ms, about 0.7 of a single cycle, which is not enough to measure a period reliably.

The Bass Tuner solves it by low-passing and decimating the buffer by a factor of 4 to an 11.025 kHz effective rate, so the same 1,024 samples cover about 93 ms and span multiple full cycles of B0. The low-pass also strips hi-hat, fret noise and pick attack that would otherwise dominate the correlation, and readings below the tuned floor of the instrument are rejected so room rumble cannot drag the needle.

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6. Why Phone Microphones Struggle Below 100 Hz

A phone capsule is not a measurement microphone. It is ported to reject wind and handling noise, and that porting acts as a high-pass filter somewhere in the 100 to 200 Hz region:

• With a first-order corner at 100 Hz, a 41.20 Hz fundamental arrives about 8 dB down (41.20 / √(41.20² + 100²) = 0.381).
• With a 200 Hz corner, the same fundamental arrives about 14 dB down.

When the fundamental is attenuated that far, the detector is working from the harmonics. Room noise makes it worse: HVAC and traffic energy peaks in the 30 to 80 Hz band, and 50 or 60 Hz mains hum sits within a few hertz of A1 = 55.00 Hz.

Practical fixes:

• Pluck firmly and let the note ring for two seconds; do not repeat-pluck.
• Hold the phone 20 to 30 cm from the speaker, away from vents and air conditioning.
• If the room is noisy, use a clip-on tuner or tune from a DI signal.
• If the reading flips between B0 and B1, tune against the 12th-fret harmonic (one octave up), then check the open string by ear.

The limits are physical, not a flaw in the app: see Why Smartphones Cannot Reproduce 20 Hz for the loudspeaker side of the same problem.