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Plectrum Theory

Essential theory for guitar players.

Short lessons that help you speak the language of music, taught on the fretboard rather than the page. Seventy-three of them, plus a reference you will keep going back to.

Coming to the App Store

iPhone. Requires iOS 17 or later.

Five sections, thirteen modules, seventy-three lessons.

The curriculum runs from naming the strings to playing over changes. Work straight through it, or drop into the section you need.

  1. 01

    Foundations

    The Basics · Notes on the Fretboard · Intervals

    15 lessons
  2. 02

    Scales and Keys

    Scales · Keys and Key Signatures

    10 lessons
  3. 03

    Chords

    Triads · Common Chord Shapes · The CAGED System · Sevenths and Extensions

    24 lessons
  4. 04

    Harmony

    Diatonic Harmony · Progressions and Movement

    12 lessons
  5. 05

    Improvisation

    Improvisation · Advanced Improvisation

    12 lessons

And a reference you will keep going back to.

Notes on the Fretboard
Find every position of any note across the neck
Intervals
The 13 basic intervals plus the most common extensions
Scales
Diatonic modes, pentatonics, melodic and harmonic minor
Chords
Triads, sixths, sevenths, and extended qualities
CAGED Shapes
The five shapes that tile the neck: C, A, G, E, D
Common Chord Progressions
Pop, jazz, blues, and the classical cadences

What is in it

Seventy-three lessons
Thirteen modules across five sections: Foundations, Scales and Keys, Chords, Harmony, and Improvisation. Each lesson is short and marked beginner, intermediate or advanced, so you can start where you actually are.
Taught on the neck
Lessons carry live fretboard diagrams, interval maps and circle of fifths diagrams. You see where a thing sits under your fingers, not staff notation you have to translate first.
Check yourself
Multiple choice questions at the end of a lesson, so you find out whether it landed before you move on.
A reference you will keep using
Six catalogs: every position of every note on the neck, thirteen intervals plus the common extensions, eleven scales, nineteen chord qualities from triads to thirteenths, the five CAGED shapes, and thirteen progressions from I-IV-V to the Andalusian cadence.
Your progress stays on your device
Completed lessons, bookmarks and quiz answers are stored locally. No account, no sign-in, nothing uploaded.
No streaks, no scores
There is no gamified system pushing you to open the app. Read a lesson when you want one, bookmark what you want to come back to, and go and play.

Worth knowing

  • Written for six string guitar in standard tuning.
  • Everything is included. No lessons are locked behind a further purchase.
  • Works entirely offline. Nothing to download after you install it.
  • Dark interface throughout. There is no light mode.
Coming to the App Store