StringLogic is built around one belief: the guitar makes sense once you can see it. This book is the long-form companion to the app — explanations, diagrams, tabs, and drills, organized so you can read it cover-to-cover or dip into any topic.

A standard guitar has six strings, tuned (from thickest to thinnest) to E – A – D – G – B – E. Knowing where each one lives is the foundation of everything in this book.

The fretboard is a grid: six horizontal strings crossed by metal frets. Press a string between two frets and you raise its pitch by a precise amount called a semitone.

Find any open string. Now press the same string at fret 12 — it is the same note, one octave higher. That's why fret 12 has two inlay dots: it is the visual midpoint of the playing range, and the moment the neck pattern starts repeating.

Tablature, or tab, is a six-line shorthand for the six guitar strings. The top line is the high E, the bottom line is the low E, and the numbers tell you which fret to press.

e|----------------------------------|
B|---------------------3------------|
G|-------------0--2-------2--0------|
D|-----0--2-------------------------|
A|--2-------------------------------|
E|----------------------------------|

All Western music — every chord, every scale, every solo — is built from a tiny alphabet of just twelve notes that repeat forever. Learn these twelve and you have the building blocks for the rest of the book.

That sequence is called the chromatic scale. After B, the pattern starts over at C — one octave higher. The black keys of a piano are the sharps (and flats); on a guitar there are no colour clues, just frets.

An interval is the distance between two notes, measured in semitones. Every chord and every scale is defined by the pattern of intervals stacked on top of a starting note (the root).

Throughout StringLogic, every interval gets its own colour. Roots are red, fifths are blue, the tritone is purple — so the moment you see a fretboard diagram, you can tell what role each note is playing.

Standard tuning is not arbitrary. Five out of six string intervals are a perfect fourth (five frets); only the G-to-B gap is a major third (four frets). That one oddity is responsible for almost every "weird" chord shape on the guitar.

You don't have to memorise every fret. Learn two octave shapes and you can find any note on any string starting from a note you already know.

The two lowest strings are where most chord roots live, so it pays to memorise their note names. The natural (no-sharp) notes always sit at the same frets across both strings — just shifted by their tuning.

A chord box is a vertical mini-map of the first few frets. Vertical lines are strings (low E on the left, high E on the right). Horizontal lines are frets. Dots tell you where to put your fingers.

Three small symbols carry most of the information in a chord diagram. Get fluent in them and you can read any voicing in a guitar book.

These eight shapes are the backbone of folk, rock, country, pop and a million campfire sing-alongs. Learn them clean and you can play tens of thousands of songs.

Add a dominant 7th and a chord goes from "resolved" to "wanting to move". These are the bedrock of blues, country and early rock and roll.

Bar  1: E7 ||  Bar  2: E7 ||  Bar  3: E7 ||  Bar  4: E7
Bar  5: A7 ||  Bar  6: A7 ||  Bar  7: E7 ||  Bar  8: E7
Bar  9: B7 ||  Bar 10: A7 ||  Bar 11: E7 ||  Bar 12: B7

The same fingers, moved by a single fret, can create suspended and major-7 colours that bring nuance to a simple progression.

A barre chord is a fixed finger shape with your index finger flattened across all six (or five) strings, acting as a movable nut. Slide it up one fret and the chord changes by one semitone. Two shapes will cover you for every key in music.

The A-shape barre puts the root on the 5th string, freeing the lowest string to be muted. It's perfect for chords whose roots are higher than F on the 6th string, because you don't have to stretch as far up the neck.

A triad is three notes — a root, a third and a fifth — stacked together. Tweak either the third or the fifth and you get four distinct moods.

Add a fourth note — a seventh — and the triad becomes a seventh chord. Suddenly you have access to the harmonic vocabulary of jazz, soul, R&B and the more sophisticated corners of rock.

Beyond the 7th lies a whole zoo of "colour" chords. Most of them simply add one extra interval (a 9, 11 or 13) on top of a triad or seventh.

A scale is just a pattern of intervals that, when applied to a starting note, produces a family of related pitches. Change the starting note and the same pattern gives you the same scale in a different key.

Lower the 3rd, 6th and 7th of a major scale by one semitone and you have its natural minor. The two scales share all the same notes if you start them on different roots — they are called relative keys.

Patterns repeat across the neck. The C major scale in the first position uses mostly open strings; play the exact same intervals starting at fret 12 and you get C major an octave higher.

Take a natural minor scale, throw away the most "wrong-sounding" notes (the 2nd and the 6th), and you're left with five notes that fit beautifully over almost any rock or blues progression.

Add a single passing note — the ♭5 ("blue note") — to the minor pentatonic and you have the blues scale. That one note is responsible for the slinky, vocal quality of blues lead playing.

e|--------------------------------|
B|-----------5b7--5---------------|
G|------5-7---------7-5-----------|
D|--7-------------------7-5-------|
A|------------------------------7-|
E|--------------------------------|

The major pentatonic is the cousin of the minor pentatonic — same shape, played three frets lower. It's the sound of country, bluegrass, and major-key rock solos.

The seven modes are just the major scale started from each of its seven notes. Same notes, different "home" — and the change of home note completely changes the emotional gravity of the music.

Compare every mode to its parallel major or natural-minor (same root). The difference is always one or two intervals — these are the notes that give each mode its identity.

A scale only becomes a mode when the music keeps coming home to that mode's root. Play A natural-minor over a vamp in C major and you'll still hear C major — because the harmony anchors C as home.

An arpeggio is a chord played one note at a time. Where a chord stacks the notes, an arpeggio rolls them out across the neck — which makes arpeggios the perfect improvisational tool for "playing the chord changes".

Arpeggios can be played in any order, but a few classic patterns will get your hands and ears moving quickly.

e|------------0--3--|
B|---------1--------|
G|------0-----------|
D|---2--------------|
A|3-----------------|
E|------------------|

e|-----------------------5--|
B|--------------------5-----|
G|---------------5----------|
D|------------7-------------|
A|------3--7----------------|
E|--5-----------------------|

The phrase "playing the changes" means outlining each chord in a progression with its own arpeggio, rather than running one scale over everything. It's the secret weapon of jazz, bebop and country lead playing.

         Dm7              G7              Cmaj7
e|----------5-----|---------7-----|---------7----------|
B|------6-----6---|-----8-----8---|-----8-----8--------|
G|--5-----------5-|-7----------7--|-9------------------|
D|----------------|---------------|--------------------|
A|----------------|---------------|--------------------|
E|----------------|---------------|--------------------|

CAGED is a system that names five movable chord shapes after the five open-position chords you already know: C, A, G, E, D. Strung together, these five shapes cover every fret on the neck — for any chord, any key.

Here are the five voicings of a C major chord. The shape on the left is the open-position C you've known forever; the rest are the same chord, climbing the neck.

CAGED isn't just for major. The same five shapes have minor, 7th, maj7, m7 and diminished cousins. Once you know the major C-shape, learning the minor C-shape is mostly a matter of flattening the 3rd.

The real power of CAGED is in connecting chord shapes to scale shapes. Each of the five CAGED voicings sits inside its own scale box — so the moment you know which CAGED shape a chord is, you also know which scale shape to solo out of.

Stack a third on every note of the major scale, and you get seven chords that belong together. These are the diatonic chords of the key, and they are the source of almost every progression in popular music.

These seven progressions, between them, account for an absurd percentage of popular songs ever written. Learn to recognise them and you can pre-hear a song after one or two bars.

The seven diatonic chords aren't equals. They fall into three functional roles that explain why some progressions feel like home and others feel restless.

The Workshop page does this for you live, but it's good to know what it's doing underneath: given a chord progression, figure out the most likely key.

Standard tuning is a great compromise — but it isn't always the best fit. Open tunings re-tune the strings so that strumming the open strings sounds a complete chord. The trade-off: you get effortless slide work and gorgeous resonance, in exchange for re-learning your fretboard.

In Open D, the six strings spell a D major chord: D - A - D - F# - A - D. Strum without fretting anything and you have D major. Barre any fret and you have a major chord at that fret.

Open E has the exact same interval structure as Open D, just tuned a whole step higher: E - B - E - G# - B - E. That extra brightness made it the go-to tuning for Duane Allman and other slide masters.

A guitar that's even slightly out of tune will sabotage everything else you've worked on. The built-in tuner uses your microphone and an autocorrelation pitch detector to tell you which note you played and how far you are from in-tune, in cents.

Time is the one thing every listener notices, even those who can't tell a major 7 from a minor 9. The metronome on the Practice page gives you a downbeat-accented click in 2/4, 3/4, 4/4 or 6/8, plus tap-tempo and BPM presets.

Every chord quality supported in the StringLogic app, with its interval recipe and example notes from a C root.

Every scale in the encyclopedia, with its interval formula and notes in C.

Quick reference for every tuning supported in the app.

You've reached the end of the book. The real work begins now — on the guitar, with the app, and with the music you love.