Introduction
Neutral thirds tuning is an alternate tuning for guitar and bass, making it possible to play quartertones on a guitar you already own.
- Unusual consonances: 5 (add 9↑11), subminor (near-equal) pentatonic scale, neutral ninth, neutral triad, small triad (4add↓♭3), subminor seventh, subminor 7th
- Crushing new dissonances: subminor 9th, sub octave, super 5th, sub 5th, supermajor 3rd, quartertone
This is the easiest way into microtonality for a guitarist, so grab an instrument and follow this quick and practical guide!
How to tune up
The diagrams below are interactive; click on them to hear the tuning. Tune your instrument to match what you're hearing.
On this page, pitches have been notated with ups and downs:
- ↑ (up) means 50 cents sharp. For example A↑ is 50 cents sharp of A.
- ↓ (down) means 50 cents flat. For example B♭↓ is 50 cents flat of B♭.
6-string guitar
| String | Pitch | Frequency |
|---|---|---|
| Highest | B↑3 | 254.178Hz |
| G♯3 | 207.652Hz | |
| E↑3 | 169.643Hz | |
| C♯3 | 138.591Hz | |
| A↑2 | 113.223Hz | |
| Lowest | F♯2 | 92.499Hz |
7-string guitar
| String | Pitch | Frequency |
|---|---|---|
| Highest | B↑3 | 254.178Hz |
| G♯3 | 207.652Hz | |
| E↑3 | 169.643Hz | |
| C♯3 | 138.591Hz | |
| A↑2 | 113.223Hz | |
| F♯2 | 92.499Hz | |
| Lowest | D↑2 | 75.567Hz |
4-string bass
5-string bass
| String | Pitch | Frequency |
|---|---|---|
| Highest | E↑2 | 84.822 Hz |
| C♯2 | 69.296 Hz | |
| A↑1 | 56.612 Hz | |
| F♯1 | 46.249 Hz | |
| Lowest | D↑1 | 37.784 Hz |
A note about string gauges
This tuning is different enough from standard that you may notice a change in string tension. Specifically, the low strings are tuned higher so they may feel more tense, whereas the high strings are tuned lower so they may feel more slack.
Try the standard set of strings first and it might work fine for you. However if you do run into tension issues, you can swap out single strings for other gauges.
Chord and scale charts
This interactive chart explorer shows where various chords and scales can be played on the fretboard.
Note layout
This interactive note finder shows where all 24 pitches can be found on the fretboard.
Listening list
Table of intervals
| Name | Quartertones | Semitones | Cents |
|---|---|---|---|
| perfect unison | 0 | 0 | 0 |
| super unison, subminor 2nd | 1 | 0.5 | 50 |
| minor 2nd | 2 | 1 | 100 |
| neutral 2nd | 3 | 1.5 | 150 |
| major 2nd | 4 | 2 | 200 |
| supermajor 2nd, subminor 3rd | 5 | 2.5 | 250 |
| minor 3rd | 6 | 3 | 300 |
| neutral 3rd | 7 | 3.5 | 350 |
| major 3rd | 8 | 4 | 400 |
| supermajor 3rd, sub 4th | 9 | 4.5 | 450 |
| perfect 4th | 10 | 5 | 500 |
| super 4th, sub tritone | 11 | 5.5 | 550 |
| tritone | 12 | 6 | 600 |
| super tritone, sub 5th | 13 | 6.5 | 650 |
| perfect 5th | 14 | 7 | 700 |
| super 5th, subminor 6th | 15 | 7.5 | 750 |
| minor 6th | 16 | 8 | 800 |
| neutral 6th | 17 | 8.5 | 850 |
| major 6th | 18 | 9 | 900 |
| supermajor 6th, subminor 7th | 19 | 9.5 | 950 |
| minor 7th | 20 | 10 | 1000 |
| neutral 7th | 21 | 10.5 | 1050 |
| major 7th | 22 | 11 | 1100 |
| supermajor 7th, sub octave | 23 | 11.5 | 1150 |
| perfect octave | 24 | 12 | 1200 |
Theory
Quartertones
The quartertone scale (also known as 24edo) divides the octave into 24 equal sized intervals. This is an exact doubling of the familiar 12-note chromatic scale.
In neutral thirds guitar tuning, the interval between each string becomes 7 quartertones, or 3.5 semitones, also known as a neutral third. This allows a guitar access to all 24 quartertones without any modification to the fretboard or needing to purchase a specialist microtonal guitar. In this system, each string has access to only 12 of the 24 notes. As you alternate through the strings, you alternate through these two sets of 12 notes.
Neutral diatonic system
Neutral diatonic is a tonal system that is particularly well suited to the physical limitations of neutral thirds tuned guitar. The open strings directly correspond to these scales, making them easy to learn and play.
While standard diatonic scales contain 5 wholetones and 2 semitones, neutral diatonic scales contain 3 wholetones and 4 ¾tones.
Each neutral diatonic scale is the average of two standard diatonic scales:
| Diatonic modes | As step sizes (semitones) | Neutral diatonic modes | As step sizes (quartertones) |
|---|---|---|---|
| Aeolian + Ionian | 2 1 2 2 1 2 2 + 2 2 1 2 2 2 1 |
Neutral Lydian | 4 3 3 4 3 4 3 |
| Locrian + Dorian | 1 2 2 1 2 2 2 + 2 1 2 2 2 1 2 |
Neutral Phrygian | 3 3 4 3 4 3 4 |
| Ionian + Phrygian | 2 2 1 2 2 2 1 + 1 2 2 2 1 2 2 |
Neutral Dorian | 3 4 3 4 3 4 3 |
| Dorian + Lydian | 2 1 2 2 2 1 2 + 2 2 2 1 2 2 1 |
Neutral Hypolydian | 4 3 4 3 4 3 3 |
| Phrygian + Mixolydian | 1 2 2 2 1 2 2 + 2 2 1 2 2 1 2 |
Neutral Hypophrygian | 3 4 3 4 3 3 4 |
| Lydian + Aeolian | 2 2 2 1 2 2 1 + 2 1 2 2 1 2 2 |
Neutral Hypodorian | 4 3 4 3 3 4 3 |
| Mixolydian + Locrian | 2 2 1 2 2 1 2 + 1 2 2 1 2 2 2 |
Neutral Mixolydian | 3 4 3 3 4 3 4 |
Each step of a neutral diatonic mode can be the root of a root-third-fifth triad. This results in 5 neutral triads, and two variants of diminished triad.
| Neutral Hypolydian | |
|---|---|
| 1 | Neutral |
| 2 | Neutral |
| 3 | Neutral |
| 4 | Diminished (0-350-650) |
| 5 | Neutral |
| 6 | Diminished (0-300-650) |
| 7 | Neutral |
Maqam, Makam and Dastgah modal systems
Maqam, Makam and Dastgah are related modal traditions from the Arabic, Turkish and Persian worlds. While the size of the quartertones vary in practice, neutral thirds tuning provides an accessible entry point for exploring (24edo approximations of) these systems on guitar.
This page's scale explorer displays the pitch content extracted from maqamat but doesn't show you how to use them. If you're exploring these modal systems, don't simply rely on what is displayed on the chart and be sure to get further information from another resource such as Maqam World.
Semaphore scale system
The 9 note variant of semaphore is a powerhouse of subminor and supermajor chords. This scale is built from a sequence wholetones and quartertones. The symmetrical mode is T-q-T-q-T-q-T-q-T.
Harmonically, each of the 9 notes can be the root of two root-third-fifth style triads. The qualities of chord are subminor, supermajor, minor, major and two variants of diminished chord. This scale completely avoids neutral intervals.
Isomorphism
In standard tuning, chord or scale shapes that you learn in one position can't be moved arbitrarily across other strings. This is because standard tuning is not regular, using the intervals P4-P4-P4-M3-P4 between strings. Neutral thirds tuning is regular, using intervals n3-n3-n3-n3-n3, therefore it is isomorphic, meaning that chord or scale shapes you learn can be moved arbitrarily anywhere on the fretboard. This makes it easier to memorise shapes and more intuitive.
Intermodulation and the new power chords
Under distortion, playing two (or more) strings at the same time results in intermodulation. This adds additional frequencies to the signal which are highly dependent on the interval being played.
When an interval is close to a simple frequency ratio, the combination tones align and the resulting sound is clean. This is why intervals like the perfect fourth, perfect fifth and octave work so well under high distortion.
Intervals that are not close to a simple frequency ratio, such as the equal-tempered minor and major thirds, result in a mess of combination tones that make the sound muddy and unstable.
With neutral thirds tuning, you get two new power chords which are easy to play as double stops and work well on the high strings - the subminor third and neutral third. Both sound great as power chords, likely due to how well 24edo approximates the simple ratios of 15/13 and 11/9 respectively.
Disadvantages
While neutral thirds tuning makes some things easier to play (the new intervals) it also makes some things harder to play (major and minor chords among others). You need to work around the limitations.
Each string only has access to 12 of the 24 notes. Techniques such as trills, slides and hammer-ons require fretting a string that's already vibrating, therefore these techniques can't be used on the new 12 intervals, only the original 12.
The range of the guitar is reduced when using neutral thirds tuning. This is the tradeoff for higher melodic density.
| Standard tuning (6 string) |
Neutral thirds tuning (6 string) |
Neutral thirds tuning (7 string) |
|
|---|---|---|---|
| Highest note | E6 | B↑5 | B↑5 |
| Lowest note | E2 | F♯2 | D↑2 |
| Total range | 4 octaves | 3 octaves + 5.5 semitones | 3 octaves + 9 semitones |
| Melodic density | 12 notes per octave | 24 notes per octave | 24 notes per octave |
Further reading
- ixlramp - Neutral thirds tuning for quartertones on conventionally fretted guitar
- Trauma Triad - Visceral Defects - Prologue and Tablature
- Xenharmonic Wiki - Guitar
- Xenharmonic Wiki - Skip fretting
- 7 String Guitar forum topic
- Xenharmonic Wiki - 24edo scales
- Maqam World - learn the Maqam modal system
- Xenharmonic Wiki - 3L 4s
Beyond neutral thirds
There are yet more alternate tunings that let you play microtones on a standard fretted guitar.
The tunings given below deviate minimally from neutral thirds tuning, for ease of switching back and forth between the microtonal options on this page.
Alternating (near-just) major and minor thirds
Ixlramp suggests a string tuning which alternates (near-just) major and minor thirds.
- Major and minor chords sound clear and crunchy under high gain and distortion, in the same way that power chords do, without getting muddy.
- You'll find 24 pitches on the fretboard, but they are not equal like quartertones. Consider this tuning to be two sets of 12 pitches, the sets offset by approximately 15 cents.
- The major and minor thirds are nearly pure, with only a tiny amount of tempering to adjust for the 700 cent fifths.
6-string guitar
7-string guitar
4-string bass
5-string bass
Harmonic series subset
Try using a subset of the harmonic series as an open string tuning, such as 4:5:6:7:9:11:12 for 7 string or 4:6:7:10:11:12 for 6 string.
- Strumming the open strings results in a power chord that can handle gain while retaining clarity, but intensely colourful with the presence of the 11th harmonic.
- Would work great on lap steel or any other guitar you want to try it on.
6-string guitar
7-string guitar
4-string bass
5-string bass
Glossary
- cent
- 1/100th of a semitone.
- down (↓)
- 50 cents flat.
- interval
- The distance between two pitches.
- neutral
- The quality of being half way between minor and major.
- neutral third
- An interval with size 350 cents, exactly half way between a minor third and major third. Two neutral thirds add up to a perfect fifth.
- quartertone
- An interval with size 50 cents, exactly half of a semitone.
- semitone
- An interval with size 100 cents. In standard tuning this is the smallest step size of the chromatic scale.
- tuning (verb)
- The act of setting up an instrument so that it can play desired pitches.
- tuning (noun)
- A set of desired pitches that an instrument can be tuned to play.
- up (↑)
- 50 cents sharp.