MICROTONAL GUITAR REFERENCE
Microtonal Guitar Fret Layouts
12-TET, full 24-TET, the Q15 layout and selective microtonal fretboards
There’s more than one way to build a microtonal guitar fretboard. Some layouts put a quarter-tone fret between every standard fret. Others add microtonal positions only over part of the neck, or use a fixed selection of positions to create a particular fret pattern.
The differences can look complicated at first. They’re easier to understand when you start with the fretboard you already know.
THE STARTING POINT
The fretboard you already know
A conventional guitar uses 12-tone equal temperament, or 12-TET. The octave is divided into 12 equal steps, or semitones. Each fret moves the pitch up one of those steps, and the pattern repeats at the octave on fret 12.
A quick note about cents: pitch differences are sometimes measured in cents. In 12-TET, one semitone is 100 cents. Half of that interval is 50 cents, the quarter-tone step used in 24-TET. Guitarists do not usually think in cents while playing, but the measurement is useful for describing exactly what “quarter tone” means.
This standard fretboard is also the starting point for the layouts below. In each case, the 12-TET fret positions can remain in their conventional locations. The difference is what happens between those positions.
QUARTER TONES
Put another fret between the frets
24-tone equal temperament, or 24-TET, divides the octave into 24 equal pitch steps rather than 12. Each conventional semitone is divided into two equal steps, creating a quarter-tone position between adjacent 12-TET notes.
The original 12-TET positions don’t disappear. They’re part of the 24-TET grid. The additional frets make the pitches between them directly playable.
THE Q15 LAYOUT
Quarter-tone positions through fret 15.
A full 24-TET fretboard places an added quarter-tone position between each adjacent pair of standard positions throughout the neck. Because the physical distance between fret positions decreases toward the bridge, the added frets are closer together in the upper register.
The Q15 layout adds a quarter-tone position between each standard position from 0 through 15. Standard positions 16 through 21 continue above the added-fret range.
INTERTONAL™ Q15™
Q15: 15 added quarter-tone positions
Q15™ is a bolt-on replacement neck. It retains all 21 standard 12-TET fret positions and adds 15 consecutive quarter-tone positions from 0.5 through 14.5, one between each standard position from 0 to 15. Standard frets 16–21 remain. The result is 36 total fret positions: the 21 standard positions plus 15 added quarter-tone positions.
The Q15 layout contains 15 added quarter-tone positions through standard fret 15. Standard frets 16–21 remain at their conventional positions.
Why Q15? Q is for quarter tone. 15 marks the extent of the added quarter-tone fret pattern: 15 additional positions through standard fret 15.
A SELECTIVE APPROACH
You don’t have to use every microtonal position
A microtonal fretboard doesn’t have to contain every possible intermediate fret.
A selective microtonal fret layout retains the conventional fret positions but adds only a fixed set of intermediate positions. That creates a particular set of microtonal interval relationships without filling the fretboard with every available quarter-tone fret.
INTERTONAL™ NUCLEAR FUSION EDITION
A fixed KGLW-inspired pattern
Nuclear Fusion Edition is a bolt-on replacement neck. It retains all 21 standard 12-TET fret positions and adds 8 fixed positions: 1.5, 3.5, 4.5, 6.5, 8.5, 10.5, 13.5 and 15.5. The design takes inspiration from the microtonal fret approach associated with KGLW.
The added positions are 1.5, 3.5, 4.5, 6.5, 8.5, 10.5, 13.5 and 15.5. Each “.5” marks a pitch position halfway between adjacent 12-TET fret numbers. Fret placement is calculated from scale length, so the physical distance between fret wires is not simply halved. The pattern ends at 15.5; standard fret positions 16–21 continue above it.
THE CAPO CHANGES THE RELATIONSHIPS
Same frets. Different interval palette.
A capo does something especially interesting on a selective microtonal fretboard. The capo moves the effective nut, but the added microtonal frets remain fixed in their original physical locations.
On a conventional 12-TET fretboard, the interval pattern simply repeats from the new starting point. On a selective layout, the standard scale pattern moves with the capo while the sparse added frets do not. Their relationship to the new tonic therefore changes.
The comparison below uses standard E–A–D–G–B–E tuning and follows only the low E string so the geometry is easy to see. With no capo, the reference is an E major scale. Add a capo at fret 1 and that same string begins on F, so the reference becomes F major.
CONTINUOUS VS. SELECTIVE
Two different ways to add notes between the notes
Q15™ uses a continuous pattern
Every quarter-tone position is present through a defined region of the fretboard. The added pattern continues consecutively through standard fret 15.
Nuclear Fusion Edition uses a selective pattern
The eight KGLW-inspired additions occur at positions 1.5, 3.5, 4.5, 6.5, 8.5, 10.5, 13.5 and 15.5.
Neither approach changes the location of the standard frets.
| Layout | Standard positions | Additional positions | Pattern |
|---|---|---|---|
| Standard 12-TET | Retained | None | Conventional |
| Full 24-TET | Retained | Every quarter-tone position | Continuous throughout |
| Hybrid / Q15™ | Retained | 15 quarter-tone positions | Continuous through standard fret 15 |
| Selective / Nuclear Fusion | Retained | 8 microtonal positions through 15.5 | Fixed KGLW-inspired pattern |
These aren’t the only ways to build a microtonal guitar. Alternative temperaments, movable frets, fretless instruments and other custom fret systems open up many more possibilities. These four layouts cover the approaches most directly relevant to InterTonal replacement necks.
WHERE TO START
Different layouts invite different experiments
12-TET
The standard reference point: twelve equal pitch steps per octave and one semitone per fret.
Full 24-TET
A continuous quarter-tone grid across the neck, with an intermediate pitch available between every standard semitone position.
Hybrid quarter-tone
A continuous run of quarter-tone positions over part of the neck, with conventional spacing elsewhere.
Selective microtonal
A fixed subset of added positions, creating a particular interval palette rather than filling every possible intermediate position.
Start with a sound that makes you curious.
Try the added positions and see where they lead.
TERMINOLOGY
Microtonal guitar FAQ
What does microtonal mean?
Microtonal music uses pitches or intervals that fall outside the conventional 12-TET pitch grid. Quarter tones are one of many approaches to microtonal music.
What is a quarter-tone guitar?
In the context of 24-TET, a quarter-tone guitar adds pitch positions halfway in pitch between conventional 12-TET semitones. A full 24-TET fretboard provides those positions throughout the fretboard.
Are microtonal and quarter-tone the same thing?
No. Quarter tones are one microtonal approach. Microtonal music can use many other interval systems, temperaments and fret arrangements.
Do you lose the normal notes when quarter-tone frets are added?
Not in the layouts shown here. The conventional 12-TET fret positions remain where they normally are; additional frets create more positions between them.
Are quarter-tone frets physically halfway between standard frets?
Fret positions are calculated from scale length. A quarter-tone pitch lies halfway in pitch between adjacent semitones; its physical position is calculated from the scale rather than by measuring halfway between two fret wires.
How does Q15 compare with a full-neck 24-TET layout?
A full-neck 24-TET layout adds a quarter-tone position between every adjacent pair of standard positions. Q15 adds 15 consecutive quarter-tone positions through standard fret 15, with standard positions continuing through fret 21.
What is a selective microtonal fret layout?
In this guide, it means a fretboard that keeps the standard fret positions and adds only a fixed selection of intermediate microtonal positions rather than every possible quarter-tone position.
What is the Q15 layout?
Q15 is InterTonal’s bolt-on replacement neck with 21 standard 12-TET fret positions plus 15 consecutive quarter-tone positions from 0.5 through 14.5. Standard positions 16–21 continue above the added-fret range.
How does a capo affect a selective microtonal fretboard?
The capo changes the effective open-string reference while the added microtonal frets remain physically fixed. As a result, those fixed frets create different interval relationships relative to the capoed tonic and scale.
INTERTONAL™
For the microtonal curious.
PARTIAL QUARTER-TONE
Q15™
The Q15 layout pairs 21 standard fret positions with 15 consecutive quarter-tone positions from 0.5 through 14.5.
Explore Q15™SELECTIVE MICROTONAL
Nuclear Fusion Edition
21 standard fret positions plus eight selective additions at 1.5, 3.5, 4.5, 6.5, 8.5, 10.5, 13.5 and 15.5. The design takes inspiration from the microtonal fret approach associated with KGLW.
Explore Nuclear Fusion© 2026 InterTonal. All rights reserved. InterTonal and Q15 are trademarks of InterTonal.