Interval Spotter

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Difficulty

m3 · M3 · P4 · P5 across adjacent string pairs.

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Ready when you are

Pick a difficulty, then start the session. Answer as many as you like — your streak saves locally.

Train interval shapes across guitar string pairs. The trainer highlights a root note on one string; you click the target interval on the adjacent string. The shapes are simple — except across the G→B boundary, which is the whole point.

How to practice

Drill one interval at a time across all five string pairs. Then move to the next.
Spend extra time on G→B. Every interval gains a fret there; treat it as a separate (smaller) memorisation task.
Verify with audio. Use the Intervals ear-trainer to confirm what each shape sounds like — connect the visual to the audible.
Build chords from intervals. Once shapes are automatic, try spelling a chord (e.g. F major from a root on D string fret 3) by stacking shapes: F (root), A (M3, G string fret 2), C (P5, B string fret 1). The "fret 1" instead of "fret 0" is the G→B offset in action.
Don't memorise inverted shapes yet. Stick with root-on-bottom for v1. Inversions (3rd on bottom, 5th on bottom) are a follow-up skill.

Common stumbling blocks

Inverting a string pair. D→A is not the same as A→D — direction matters because the lower note must be the root. Always start with the lower string.
Treating the B-string offset as a bug. It's a feature of standard tuning that keeps chord shapes ergonomic. Without it, barre chords would be impossible. Accept it.
Skipping the high-e pair. Many learners never drill B→e. It comes up constantly in jazz comping; don't skip it.

The intervals in this trainer

Difficulty	Pool
Beginner	m3 · M3 · P4 · P5
Intermediate	adds m6 · M6 · m7 · M7
Advanced	adds TT · m9 · M9 · P12 — and reverses direction

Intervals beyond P5 sometimes have to cross two strings (e.g. a minor 7th between the low E and D strings is wider than four frets). The trainer handles this; the visualizer above stays on adjacent pairs for simplicity.

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Fretboard Intervals

Same interval, five shapes

Pick an interval and see how its shape changes across each adjacent string pair. Four pairs use one shape — the G→B pair shifts by one fret because the tuning narrows there.

E → A+2 frets

A → D+2 frets

D → G+2 frets

G → B+3 frets

B → e+2 frets

Root note sits on fret 3 of the lower string in each diagram. The offset label above each diagram (+5 frets, +4 frets, etc.) is the distance from the root to the target on the higher string. Notice how G→B is always one fret different from the other four.

What an interval shape is

On guitar, an interval shape is the geometric pattern that produces a given interval between two notes on adjacent strings. A minor 3rd is "down one string, down one fret" — except on the G→B pair, where it's "down one string, same fret".

These shapes are the building blocks of every chord, arpeggio, and melodic phrase. Once internalised, you can spell any chord on the fly without thinking about note names.

Why this trainer is harder than it looks

The B string. The cursed B string. Five of the six strings are tuned a perfect 4th apart — but G→B is a major 3rd (one semitone narrower). Every interval shape gains one fret on that pair.

The visualizer above shows all five string-pair shapes for any chosen interval side by side. Four pairs look identical; the G→B pair sits one fret over. That's the rule you're memorising.

The "+1 across G→B" rule, in one table

Interval	Standard pair offset	G→B pair offset
m3	down 1 string, down 1 fret	down 1 string, same fret
M3	down 1 string, no fret change	down 1 string, +1 fret
P4	down 1 string, same fret	down 1 string, +1 fret
TT	down 1 string, +1 fret	down 1 string, +2 frets
P5	down 1 string, +2 frets	down 1 string, +3 frets
m6	down 1 string, +3 frets	down 1 string, +4 frets
M6	down 1 string, +4 frets	down 1 string, +5 frets
P8	down 2 strings, +2 frets	down 2 strings, +3 frets

That single +1 is responsible for 90% of the "why does this chord shape look weird" frustration on guitar.

How interval shapes build chords

A major triad is just root + M3 + P5. On guitar, that's:

Root on the A string
M3 on the D string, no fret change (just down 1 string)
P5 on the G string, +2 frets

Boom — C major from a root on A string fret 3: A:3 + D:2 + G:0 (well, actually it's E:3 wait let me restate). Either way, every chord is just a stack of interval shapes. Learn the shapes, build any chord from any root anywhere on the neck.

Shapes lead to "shell voicings"

A "shell voicing" is a chord stripped down to its essential intervals — usually root, 3rd, and 7th. Jazz guitarists use them as harmonic skeletons, then add tensions on top.

min7 shell: root + m3 + m7
maj7 shell: root + M3 + M7
dom7 shell: root + M3 + m7

Build these using interval shapes and you can spell any 7th chord in any key, anywhere on the neck, without ever looking up a chord chart. That's the unlock.

FRETBOARD PRACTICE

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