Diatonic mode
Pick a key and a scale system. The table shows every chord that belongs to that harmony. Tap a row to light up the fretboard. Toggle the column headers (R 3 5 7 9 11 13) to show or hide interval groups on the neck.
V chord (G) in C Major, showing R 3 5 on the neck
Free mode
Switch to Free to build any chord from scratch: pick a root note and a quality. The fretboard lights up immediately. A reverse lookup line tells you where that chord lives diatonically, so you can work backwards from a sound you like to the theory behind it.
C7b9 in Free mode. The reverse lookup shows V in F Harmonic Minor.
Position zones (1 through 5)
The five positions are five windows on the neck, each about five frets wide, anchored to the root note on the low E string. They correspond to the five CAGED shapes: each zone contains a complete voicing of the chord in a different region of the fretboard. Together they tile the entire neck with no gaps.
Position 3 in C: frets 1 through 5
Position 1 in C: frets 8 through 12
Forbidden diagonal
Five CAGED shapes is a lot to memorise, and the boundaries between them feel arbitrary. The diagonal takes a different approach: instead of five boxes, it draws three lines that flow diagonally across all six strings, cycling through root, third, and fifth. Each line is one rotation of the same three note pattern (R 3 5, or 3 5 R, or 5 R 3), which means you only learn one shape and shift your starting point.
Three diagonal lines for G major: each flows across all six strings
The result is three flowing patterns instead of five static boxes. The lines connect positions naturally, the voice leading is built in, and moving up or down the neck becomes intuitive. Think of CAGED as geography (where am I?) and the diagonal as movement (where am I going?).
Other controls
Deg / Note — switch fretboard labels between interval degrees and note names
Tuning — Standard 6-string, drop and open tunings, extended range (7/8/9-string), or bass (4/5/6-string)
Theme — tap the theme name (top right) to randomise colours