Music Theory
The building blocks of music — from individual notes and intervals to triads, keys, and beyond. Explore topics below and connect the theory to chords, scales, and progressions on every instrument.
Use this hub to learn how notes, intervals, keys, and chord symbols work — then jump to any instrument for fretboard diagrams that match what you read here.
Practice tools
Metronome and pitch, reference articles (tunings, rhythm, chord naming), songwriting helpers, and teaching tips — all in your browser.
Practice · reference · workflowMusical Notes
All 12 semitones — frequencies, enharmonic equivalents, triads, and key relationships. The fundamental building blocks of melody and harmony.
12 notesScales & harmony by tonic
For each pitch class: parallel major and minor harmony, common progressions, related keys, and every scale type spelled from that tonic — pure theory, no diagrams.
12 keysChords in the Key of…
For every major key: the seven diatonic chords with Roman numerals, the scale, the relative minor, and common progressions — each chord linked to guitar voicings.
12 major keysScales for Chords
What scale do you play over this chord? For 360 chords: every same-root scale that contains the chord, the major keys it lives in, and guitar diagrams.
360 chordsIntervals
The distance between two notes — unison to octave and beyond. How intervals define chord quality and melodic character.
Simple + compoundCircle of Fifths
The master map of key signatures, showing how every major and minor key relates through fifths and fourths.
12 keysChord Types, Construction & Formulas
How chords are built from stacked thirds, then a transposable reference for every type — triads, sevenths, sixths, extensions, sus, diminished, augmented, and altered chords.
Interactive · all 12 rootsNashville Number System
Read and write chord charts in any key using scale-degree numbers, quality marks, and rhythm shorthand — the working language of session players.
Numbers · quality · rhythm marksCAGED System (guitar)
The five movable chord shapes — C, A, G, E, D — that map the entire guitar fretboard in standard tuning. Guitar-specific.
5 shapes · guitar onlyModes
All seven modes of the major scale — from the bright Ionian to the dark Locrian. Intervals, diatonic harmony, characteristic progressions, and scale spellings from every root.
7 modesFamous Progressions
Named chord progressions every player should know — 12-bar blues, the ‘Axis’ progression, ii–V–I, and more — with Roman numerals, linked chords in a key, and the songs that made them famous.
8 progressionsAlternate Tunings
Common alternate guitar tunings — Drop D, DADGAD, Open G, and more — with the string notes vs. standard, how to retune, and famous songs for each.
7 tuningsTheory guides & how-tos
Plain-English reference articles that connect the dots between symbols, shapes, and sound.
- How to read chord diagrams — decode the grids, dots, X and O markers, and barre lines.
- How to play barre chords — technique, the E-shape and A-shape roots, and a clean-tone troubleshooting guide.
- Best scales for blues — the blues scale, minor and major pentatonics, and how to mix them.
- The five pentatonic shapes — why a minor pentatonic and its relative major are the same five boxes, and where each one sits.
- Blues scale shapes on the fretboard — the same five boxes with the b5 added, and exactly where the blue note falls in each.
- Beginner chord progressions — the I–IV–V, I–V–vi–IV, and 12-bar blues every player should know.
- Major vs minor — the one-note difference that splits happy from sad, in chords and keys.
- How to read guitar tab — string lines, fret numbers, and what h, p, b, /, \, and x mean.
- Music glossary for beginners — plain-English definitions for diatonic, movable, voicing, barre, sus, course, interval, mode, capo, and tonic.
- Your first chords — the easiest open chords, a practice order, and encouragement for the early days.
- How to tune your instrument — standard tunings for guitar, bass, ukulele, and mandolin, by ear or with a tuner.
Connect theory to the fretboard
Instruments · Guitar chords · Guitar scales · Diatonic chords by key
Theory hub FAQ
- What is the circle of fifths for?
- It shows how keys relate by perfect fifths, how many sharps or flats each key uses, and how closely related keys share chords — essential for modulating and memorizing signatures.
- How does this tie into Nashville numbers?
- Nashville numbers label chords by scale degree in the current key. Once you know the key from the circle or your ear, the same chart works in every key.
- Where should I read about chord symbols?
- Start with Chord construction for how triads and seventh chords are built, then use your instrument’s chord library to see those qualities on the fretboard.
- Is CAGED only for guitar?
- Yes — CAGED maps movable chord shapes in standard guitar tuning. Other instruments use their own tuning-specific layouts on this site.
- Do I need to read theory before opening chords?
- No. Many players browse diagrams first. Use theory pages whenever you want names for what you are hearing or playing.