---
title: Fretboard Geometry
category: Guitar in P4
slug: fretboard-geometry
related: [fourths-tuning-overview, intervals, pentatonic-system]
url: https://fourthshub.com/docs/fretboard-geometry
---

# Fretboard Geometry

The all-fourths fretboard is a **uniform lattice** where every geometric relationship between notes is consistent across the entire instrument. This section maps out the key patterns.

## The Fundamental Principle

Each fret is one half step. Each string crossing is a perfect fourth (5 frets). Therefore, any two-dimensional shape on the fretboard represents a fixed intervallic relationship, regardless of where you place it. This is not true in standard tuning.

## Interval Shapes (Same String vs. Adjacent Strings)

On the **same string**, intervals are measured in frets:
- Minor 2nd: 1 fret
- Major 2nd: 2 frets
- Minor 3rd: 3 frets
- Major 3rd: 4 frets
- Perfect 4th: 5 frets (= one string crossing)

Across **adjacent strings** (with fret offset):
- Perfect 4th: same fret, next string up
- Tritone: same fret +1, next string up
- Perfect 5th: same fret +2, next string up
- Minor 6th: same fret +3, next string up
- Major 3rd: same fret -1, next string up
- Minor 3rd: same fret -2, next string up

## Octave Pattern

An octave is always **2 strings up, 2 frets toward the bridge**. This is the most important shape in P4 tuning. It never changes. In standard tuning, octaves shift by one fret when crossing the G-B string pair; in P4, the shape is absolutely consistent.

## Unison Pattern

The same pitch on an adjacent higher string is **5 frets lower** (toward the nut). On a string two above, it is **10 frets lower** (or equivalently, 2 frets higher).

## Diagonal Tiling

Because the tuning is uniform, any pattern **tiles diagonally** across the fretboard. A pentatonic box at fret 5 on strings 6-5 appears identically at fret 10 on strings 4-3 and fret 15 on strings 2-1. Connecting these tiles gives you full-neck coverage from a single shape.

## Symmetry Groups

Certain note collections have special symmetry on the P4 fretboard:
- **Whole tone scale**: Tiles perfectly in straight horizontal lines
- **Diminished scale**: Forms a rectangular grid pattern
- **Chromatic scale**: Every fret, every string — the complete lattice

## Practical Implications

When learning new material, always ask: "What shape is this?" Once you identify the shape, you know it works everywhere. This is the P4 advantage distilled to one principle: **learn shapes, not positions**.