GuitarTheory

What is GuitarTheory?

GuitarTheory is an application that makes music theory approachable and visual. At its core is an interactive Circle of Fifths — a fundamental map of musical relationships that musicians have relied on for centuries. Instead of reading about it in a textbook, you can explore it directly: click any key, hear how it sounds, and instantly see how it connects to other keys, chords, and scales.

The app also includes a chord diagram library, a scale visualizer, a chord progression builder, and a music theory game — all designed to help you understand the relationships between notes, not just memorize them.

Who is it for?

What's inside

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  Circle of Fifths — Explore all 12 major and 12 minor keys with audio playback and related key highlighting. Choose your guitar sound — acoustic steel, electric jazz, distortion, or overdriven — from your profile.
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  Chord Visualizer — Browse 14 chord types across all 12 keys with fingering diagrams, interval degrees, staff notation, and compatible scales. Select notes you're playing and instantly identify what chord they form — or discover extended chords that contain those same notes.
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  Scale Visualizer — See scale patterns across the neck for a broad and growing library: church modes, pentatonics, blues, jazz scales, and exotic scales from world music traditions. Supports standard and alternate tunings — DADGAD, Open G, Drop D, and more — with patterns, notation, and TAB all updating together. Save your favorites for quick reference anytime — with more scales added all the time.
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  Chord Progression Builder — Build, play, and experiment with chord progressions. Share them or save them to your account.
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  GT Game — Test your theory knowledge with a 25-level progressive quiz, including ear-training and applied-skill levels where you identify intervals, chord qualities, and fretboard notes purely by sound. Challenge a friend with a share link, or check the leaderboard to see top scores for any level.
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  Song Lab — Integrated songwriting workspace: build a chord progression, identify the key, get scale and lick suggestions, and write guitar tab with live two-voice notation. A full rhythm model handles everything from whole notes to 32nds, plus per-note ring time so a held bass can sustain under a moving melody — true counterpoint. Practice Mode auto-scrolls and highlights as it plays, with slow-down, count-in, and looping. Import/export MIDI (with faithful timing and multi-track merge), import ASCII tab, set section markers, pick your guitar sound, save licks to a personal library, and share community licks. Cross-tool buttons in the Scale Visualizer and Chord Visualizer send your selection straight into a Song Lab tab sheet.
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  Knowledge Hub — Fourteen in-depth music theory guides written for guitarists, organised into Foundations, Scales & Modes, Guitar-Specific, and Practice & Skills sections. Topics include Intervals, Chord Theory, Chord Progressions, Functional Harmony, the Nashville Number System, Modulation, Modes, Pentatonic Scales, Triads & Inversions, Arpeggios, the CAGED System, Blues Theory, the Circle of Fifths, and an interactive Ear Training studio. Every guide is interactive — pick a root note or key and the diagrams update live. Many guides include play buttons so you can hear the theory: compare a tritone against a perfect fifth, listen to a ii–V–I resolve in any key, or train your ear to recognise intervals and chord qualities by sound — all using the guitar voice from your profile.
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  Ask Assistant — A built-in help assistant: tap the 💬 Ask button in the corner of any page, type a question in plain language, and get an instant answer with direct links to the right tool or guide. It answers a wide range of music theory on the spot — the notes in any chord, the formula or notes of any scale, the chords and modes of a key, key signatures, intervals, slash chords and inversions, what key a progression is in, transposing and capo questions, even what note sits at a given fret. Every answer is computed from the same engine the app uses, so it's always correct, and it runs entirely on GuitarTheory's own engine — no third-party AI, nothing sent to an outside service. It's a focused theory helper rather than a general chatbot; see the Ask Assistant guide under How To Use for example questions.

Our philosophy

Music theory has a reputation for being dry, abstract, and hard to apply. But it doesn't have to be. The goal of GuitarTheory is simple: help guitarists understand music, not just follow tab sheets or memorize patterns.

When you understand why a chord progression sounds the way it does, or why a particular scale fits over a certain key, you stop being a player who follows instructions and start being a musician who makes choices. That's what this tool is built for.