guitar-fretboard（吉他指板）

Guitar Fretboard Visualization Skill

Create interactive React artifacts for guitar fretboard visualizations with proper music theory.

Core Music Theory Reference

Notes and Intervals

const NOTES = ['C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B']
const STANDARD_TUNING = ['E', 'A', 'D', 'G', 'B', 'E'] // low to high (6th to 1st string)

// Semitone intervals from root
const INTERVALS = {
  root: 0, minor2nd: 1, major2nd: 2, minor3rd: 3, major3rd: 4,
  perfect4th: 5, tritone: 6, perfect5th: 7, minor6th: 8,
  major6th: 9, minor7th: 10, major7th: 11, octave: 12
}

Scale Formulas (semitones from root)

const SCALES = {
  major: [0, 2, 4, 5, 7, 9, 11],           // W-W-H-W-W-W-H
  minor: [0, 2, 3, 5, 7, 8, 10],           // W-H-W-W-H-W-W (natural minor)
  majorPentatonic: [0, 2, 4, 7, 9],        // 1-2-3-5-6
  minorPentatonic: [0, 3, 5, 7, 10],       // 1-b3-4-5-b7
  blues: [0, 3, 5, 6, 7, 10],              // minor pentatonic + b5
  dorian: [0, 2, 3, 5, 7, 9, 10],          // mode 2
  phrygian: [0, 1, 3, 5, 7, 8, 10],        // mode 3
  lydian: [0, 2, 4, 6, 7, 9, 11],          // mode 4
  mixolydian: [0, 2, 4, 5, 7, 9, 10],      // mode 5
  locrian: [0, 1, 3, 5, 6, 8, 10],         // mode 7
  harmonicMinor: [0, 2, 3, 5, 7, 8, 11],
  melodicMinor: [0, 2, 3, 5, 7, 9, 11]
}

CAGED System Forms

The CAGED system uses 5 moveable chord shapes (C, A, G, E, D) that connect across the fretboard:

const CAGED_ROOT_POSITIONS = {
  // Fret offsets where root appears for each form (relative to form position)
  C: { string6: null, string5: 3, string4: null, string3: null, string2: 1, string1: null },
  A: { string6: null, string5: 0, string4: 2, string3: 2, string2: null, string1: null },
  G: { string6: 3, string5: null, string4: 0, string3: 0, string2: null, string1: 3 },
  E: { string6: 0, string5: null, string4: 2, string3: null, string2: 0, string1: 0 },
  D: { string6: null, string5: null, string4: 0, string3: 2, string2: 3, string1: null }
}

Fretboard Component Architecture

Core Helper Functions

// Get note at any fret position
const getNoteAtFret = (openNote, fret) => {
  const startIndex = NOTES.indexOf(openNote)
  return NOTES[(startIndex + fret) % 12]
}

// Check if note is in scale
const isNoteInScale = (note, rootNote, scaleFormula) => {
  const rootIndex = NOTES.indexOf(rootNote)
  const noteIndex = NOTES.indexOf(note)
  const interval = (noteIndex - rootIndex + 12) % 12
  return scaleFormula.includes(interval)
}

// Get interval name from root
const getInterval = (rootNote, note) => {
  const rootIndex = NOTES.indexOf(rootNote)
  const noteIndex = NOTES.indexOf(note)
  return (noteIndex - rootIndex + 12) % 12
}

// Get degree in scale (1-7 for diatonic, 1-5 for pentatonic)
const getScaleDegree = (note, rootNote, scaleFormula) => {
  const interval = getInterval(rootNote, note)
  return scaleFormula.indexOf(interval) + 1
}

Fretboard Layout Constants

const FRETS = 15          // Standard display: 15 frets
const STRINGS = 6         // 6-string guitar
const FRET_MARKERS = [3, 5, 7, 9, 12, 15, 17, 19, 21, 24]  // Single dot positions
const DOUBLE_MARKERS = [12, 24]  // Double dot positions

Implementation Patterns

Pattern 1: Complete Fretboard with Scale Highlighting

Display all frets with selected scale notes highlighted:

const Fretboard = ({ rootNote, scale, tuning = STANDARD_TUNING }) => {
  const scaleFormula = SCALES[scale]

  return (
    <div className="fretboard">
      {/* Nut (open strings) */}
      <div className="nut">
        {tuning.map((note, string) => (
          <NoteMarker
            key={string}
            note={note}
            isRoot={note === rootNote}
            inScale={isNoteInScale(note, rootNote, scaleFormula)}
          />
        ))}
      </div>

      {/* Frets */}
      {Array.from({ length: FRETS }, (_, fret) => (
        <div key={fret} className="fret">
          {tuning.map((openNote, string) => {
            const note = getNoteAtFret(openNote, fret + 1)
            return (
              <NoteMarker
                key={string}
                note={note}
                isRoot={note === rootNote}
                inScale={isNoteInScale(note, rootNote, scaleFormula)}
                showDegree={true}
                degree={getScaleDegree(note, rootNote, scaleFormula)}
              />
            )
          })}
        </div>
      ))}
    </div>
  )
}

Pattern 2: Pentatonic Box Patterns

Display the 5 pentatonic patterns:

// Pattern positions for minor pentatonic (frets relative to pattern start)
const PENTATONIC_PATTERNS = {
  pattern1: { // Root position (minor) / Pattern 5 (relative major)
    startFret: 0,  // relative to root
    positions: [
      [0, 3], [0, 3], [0, 2], [0, 2], [0, 3], [0, 3]  // [fret offsets per string]
    ]
  },
  pattern2: { startFret: 3 },
  pattern3: { startFret: 5 },
  pattern4: { startFret: 7 },
  pattern5: { startFret: 10 }
}

Pattern 3: CAGED Chord Forms

const CAGEDChord = ({ form, rootNote, tonality = 'major' }) => {
  // Calculate fret position based on root note and form
  const getFormPosition = () => {
    // Each CAGED form has specific root string and offset
    const formRoots = { C: 5, A: 5, G: 6, E: 6, D: 4 }
    // ... calculate position
  }

  return (
    <div className="caged-form">
      {/* Render chord shape at calculated position */}
    </div>
  )
}

Pattern 4: Triad Visualizations

const TRIADS = {
  major: [0, 4, 7],      // R-3-5
  minor: [0, 3, 7],      // R-b3-5
  diminished: [0, 3, 6], // R-b3-b5
  augmented: [0, 4, 8]   // R-3-#5
}

// String groupings for triads
const TRIAD_SETS = [
  [1, 2, 3],  // strings 1-2-3
  [2, 3, 4],  // strings 2-3-4
  [3, 4, 5],  // strings 3-4-5
  [4, 5, 6]   // strings 4-5-6
]

Styling Guidelines

Color Schemes for Notes

/* Recommended semantic colors */
.root { background: #ef4444; }      /* Red - root note */
.third { background: #22c55e; }     /* Green - 3rd */
.fifth { background: #3b82f6; }     /* Blue - 5th */
.seventh { background: #a855f7; }   /* Purple - 7th */
.blue-note { background: #06b6d4; } /* Cyan - blues note */
.scale-note { background: #6b7280; } /* Gray - other scale notes */

Fretboard CSS Structure

.fretboard {
  display: flex;
  flex-direction: row;
  background: linear-gradient(to bottom, #78350f, #451a03);
  border-radius: 4px;
  padding: 8px;
}

.string {
  height: 2px;
  background: linear-gradient(to bottom, #d4d4d4, #a3a3a3);
}

.fret-wire {
  width: 3px;
  background: #a8a29e;
}

.fret-marker {
  width: 12px;
  height: 12px;
  background: #fafaf9;
  border-radius: 50%;
  opacity: 0.3;
}

Feature Implementations

Interactive Features

1. Note Selection: Click to highlight/select notes
2. Scale Selector: Dropdown for root note + scale type
3. Pattern Navigation: Buttons to cycle through patterns
4. Audio Playback: Optional Tone.js integration for note sounds
5. Hover Information: Show note name, interval, scale degree

Display Modes

1. All Notes: Show every note on fretboard
2. Scale Only: Show only notes in selected scale
3. Intervals: Show interval numbers instead of note names
4. Degrees: Show scale degrees (1, 2, 3, etc.)
5. Patterns: Highlight specific positional patterns

Usage Examples

User Request: "Show me the A minor pentatonic scale on the fretboard" → Render fretboard with A minor pentatonic highlighted, root notes emphasized

User Request: "Create a CAGED chord diagram for C major" → Show all 5 CAGED forms for C major across the fretboard

User Request: "Visualize the 5 pentatonic box patterns in E minor" → Create 5 separate fretboard sections showing each pattern position

User Request: "Show me all the triads in G major" → Display triads on different string sets with chord quality labels

See Also

• references/scales.md - Complete scale formulas and theory
• references/caged.md - Detailed CAGED system patterns
• references/intervals.md - Interval theory and fretboard mapping