| name | guitar-fretboard-mastery |
| description | Comprehensive guitar theory consulting based on the Fret Science system by Keith Martin. Use when helping with fretboard visualization, pentatonic scales, modes, CAGED system, triads, intervals, 3nps patterns, harmonization, or any guitar theory questions. Covers the warp concept, rectangle/stack pentatonic approach, modal brightness, chord voicing analysis, and fretboard memorization techniques. Philosophy: Understand more, memorize less.
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Guitar Fretboard Mastery (Fret Science System)
A systematic approach to guitar theory emphasizing geometric patterns and understanding over rote memorization.
Core Concept: The Warp
The most important fretboard concept: the G-B string boundary shifts patterns by one fret.
- Standard tuning uses perfect 4ths (5 semitones) between strings, EXCEPT G-to-B which is a major 3rd (4 semitones)
- Any pattern crossing G↔B shifts one fret toward the bridge (G→B) or toward the nut (B→G)
- This explains why chord shapes change when moved across strings
Pentatonic Scale: Rectangle & Stack
The pentatonic scale is a 5-string repeating pattern with two geometric shapes:
The Rectangle (Red)
- Two notes on adjacent strings spanning 3 frets each
- Contains: 1, 5, b3, b7 (minor) or 6, 3, 1, 5 (major)
- Both right-hand notes can be bent a full step
The Stack (Blue)
- Three adjacent strings with 2-fret intervals
- Contains: b3, b7, 4, 1, 5 (minor) or 1, 5, 2, 6, 3 (major)
- Top-right corner bends full step; lower-right notes bend 1.5 steps
Navigation
- Rectangle and stack alternate vertically in each pentatonic form
- Rectangle and stack alternate horizontally with slight diagonal descent
- Stack connects diagonally to itself one octave higher (Clapton pathway)
Five Forms
All forms derive from shifting the 5-string repeating pattern up strings (accounting for warp):
Form 1 → Form 4 → Form 2 → Form 5 → Form 3 → Form 1
Modes: Pentatonic + Fill-in Notes
Six modes are pentatonic scales with two notes added inside the rectangle:
| Mode | Type | Fill Position | Brightness |
|---|
| Lydian | Major | Both right | Brightest |
| Ionian | Major | Staggered | Medium |
| Mixolydian | Major | Both left | Darker |
| Dorian | Minor | Both right | Brightest |
| Aeolian | Minor | Staggered | Medium |
| Phrygian | Minor | Both left | Darkest |
Locrian (b5) doesn't fit this system—it's not built on major/minor pentatonic.
Brightness Order (each differs by one semitone)
Lydian (#4) → Ionian → Mixolydian (b7) → Dorian (b3,b7) → Aeolian (b3,b6,b7) → Phrygian (b2,b3,b6,b7) → Locrian
3nps (Three-Notes-Per-String)
A 7-string universal pattern with only 3 fingering shapes:
- 1-2-4 (half-whole): Scale degrees 7, 3
- 1-3-4 (whole-half): Scale degrees 6, 2
- 1-3-5 (whole-whole): Scale degrees 5, 1, 4
Phone Numbers for String Movement
- Going UP: 7-3-6-2-5-1-4
- Going DOWN: 4-1-5-2-6-3-7
Pattern 4→7 transition shifts one fret (can combine with warp for 2-fret shift).
String Pairs (for horizontal movement)
Memorize the 7 pairs—great for melodic sequences:
- Pair 1: 4/1 → 5/2 → 6/3 (same shape as Pair 5)
- Pairs 2-7 follow sequentially
CAGED System
Five open chord shapes (C-A-G-E-D) become a pegboard for the entire fretboard.
Root Locations
Memorize where roots fall in each CAGED shape—snap any pattern onto these positions.
Layered Hierarchy (for improvisation)
- Root — Home base, most stable
- Triad (1-3-5) — Always consonant, great phrase endings
- Pentatonic — Adds melodic options
- Mode — Full color palette
Triads
Four Types (stacked thirds)
| Triad | Formula | Lower 3rd | Upper 3rd |
|---|
| Major | 1-3-5 | Major (4) | Minor (3) |
| Minor | 1-b3-5 | Minor (3) | Major (4) |
| Diminished | 1-b3-b5 | Minor (3) | Minor (3) |
| Augmented | 1-3-#5 | Major (4) | Major (4) |
Inversions
- Root position: 1-3-5
- 1st inversion: 3-5-1
- 2nd inversion: 5-1-3
Nine closed-form shapes exist (3 inversions × 3 string groups, warped versions for G-B crossing).
Quick Modifications
From Major: lower 3rd → minor, raise 5th → augmented, lower root 1 fret → maj7, lower root 2 frets → dom7
From Minor: raise 3rd → major, lower 5th → diminished, lower root 2 frets → m7
Intervals
Counting System
- Horizontal: +1 fret toward bridge, -1 toward nut
- Vertical: +5 per string up (toward floor), -5 per string down
- Warp crossing: count diagonally
Reference Table
| Semitones | Interval | Semitones | Complement |
|---|
| 0 | Unison | 12 | Octave |
| 1 | m2 | 11 | M7 |
| 2 | M2 | 10 | m7 |
| 3 | m3 | 9 | M6 |
| 4 | M3 | 8 | m6 |
| 5 | P4 | 7 | P5 |
| 6 | #4/b5 | 6 | Tritone |
9th = 2nd, 11th = 4th, 13th = 6th (subtract 7)
Harmonization with Thirds
Which Scale Degrees Get Major/Minor Thirds
- Major thirds (4 frets): 1, 4, 5
- Minor thirds (3 frets): 2, 3, 6, 7
Technique
- Play melody on one string
- Add third on adjacent string (major or minor based on scale degree)
- Keep one finger anchored, shift other finger for major/minor
Spread Thirds with Pedal Tone
Capture open string as pedal, play thirds 2+ strings away. Assign scale degree to the note matching the open string to create any modal sound.
Circle of 4ths/5ths
Vertical Movement
Moving up a string = up a 4th (clockwise on circle)
Moving down a string = down a 4th (counterclockwise)
The Sequence
4ths: B-E-A-D-G-C-F-Bb-Eb-Ab-Db-Gb
5ths: Reverse order with sharp names
Wraps diagonally around fretboard due to warp.
Fretboard Memorization Exercises
- Combine with pentatonic: Find note everywhere using octave jumps, build pentatonic each time
- Follow progressions: Find roots and build triads for each chord in a song
- Cycle of 4ths on one string: Play B-E-A-D-G-C-F-Bb-Eb-Ab-Db-Gb
- Chromatic one-note-per-string: Move chromatically while changing strings
Octave Shapes (CAGED Backbone)
Two "chess moves" for octave jumps:
- +2 strings, +2 frets (no warp) → +3, +2 with warp
- +2 strings, -3 frets (no warp) → +2, -3 with warp
These shapes connect CAGED positions.
For detailed diagrams, fingering charts, and visual references, consult the references/ folder.
