Plectrum Theory
Music Theory for Guitar
Only for iPhone
$9.99 · Designed for iPhone. Not verified for macOS.
iPhone
Learn music theory in the context of the guitar. Seventy-three concise lessons plus a reference you'll return to whenever you need it.
Music theory for guitarists, taught on the fretboard.
Most music theory is written with the piano in mind, leaving guitarists to translate every concept to the neck. Plectrum Theory starts with the guitar. Every idea is shown as something you can see, hear, and play, directly on the fretboard—so you understand how it connects, not just what it is.
THE CURRICULUM
Seventy-three lessons across thirteen modules, arranged to build naturally from the fundamentals to improvisation.
Foundations — notes on the fretboard, intervals, and the building blocks of music
Scales & Keys — scale construction, key signatures, and the modes
Chords — triads, open chords, the CAGED system, and seventh chords
Harmony — diatonic harmony and chord progressions
Improvisation — applying theory to create music
Lessons are short and focused. Each ends with a review question to reinforce what you've learned, while progress tracking and bookmarks make it easy to stop and pick up where you left off.
THE REFERENCE
A practical reference you'll keep returning to long after you've finished the lessons.
Intervals — every interval with formulas and fretboard diagrams
Scales — construction, formulas, and fretboard positions
Chords — nineteen chord qualities from triads to thirteenths, each with formulas and diagrams
CAGED — the five interconnected shapes across the neck
Progressions — the essential progressions and the harmony behind them
Fretboard Notes — every note across the neck in every key
BUILT FOR LEARNING
Every diagram is drawn on a real guitar fretboard.
Interval labels appear on every shape, making patterns understandable instead of something to memorize.
Portrait and landscape layouts.
A distraction-free dark interface designed for long study sessions.
Works entirely offline.
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The developer, DAVID TRION OTT, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
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Information
- Seller
- DAVID TRION OTT
- Size
- 1.6 MB
- Category
- Education
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Method Missing LLC
