Theory Glossary
What it’s for
The Theory Glossary is the reference behind every GMI app. Each entry is written from decades of professional playing and teaching, in plain language, for guitarists: what a term means, how it sounds, and where you’ll meet it on the neck.
It isn’t a dictionary you visit once. The apps are wired into it. Terms with a dotted underline open their definition as you work, and many entries end with a link that opens the right app on that exact subject: read about drop 2, then see every drop 2 voicing in Chord Lab a click later.
It also carries ideas you won’t find in a general glossary, among them the Protean chord, upper structures, stacking chords, inferred roots and harmonic synonyms, drawn from GMI’s own books on jazz guitar.
Who it’s for
Everyone. Beginners can look up a word they’ve just met in an app. Experienced players will find the jazz-specific material: synonyms, altered dominants, upper structure formulas, bebop language, playing outside.
Free and Pro
Free The whole Glossary is free, with or without an account.
Some of the apps an entry links to are Pro, such as Structure Lab and Progression Lab. The entry itself is always free to read.
Getting around
From the top of the page down:
- The search box filters every entry as you type.
- The category buttons jump to a section: Voicing Types, Inversions, Chord Types, Upper Structure Formulas, Voice Leading, Harmony & Function, Scales & Modes, Improvisation, Guitar Technique, Notation Basics, Intervals, and Rhythm & Feel.
- The entries, grouped by category, each with its name on the left and its definition on the right.
- ↑ Top, at the side of the screen once you scroll down, takes you back to the search box.
Features
Search
Free
- Every word must match, in any order, in the entry’s name or its definition. “Altered dominant” and “dominant altered” find the same entries.
- Flats and sharps can be typed either way. ♭9 and b9 both work, and so do ♯11 and #11.
- Spaces inside a term don’t matter. “drop2” finds Drop 2.
- Enter jumps to the first match. Esc or × clears the box and brings every entry back.
- Category buttons with no matches hide while you search, so the buttons that remain show where the matches are.
If nothing matches, the page suggests trying fewer words or a related term.
Entries and their app links
Free
Each entry explains the term in a paragraph, with the intervals or formula where it helps (Major 7th: 1·3·5·7) and a worked example (Cmaj7 = C·E·G·B).
Many entries end with a link that opens an app on that subject:
- Voicing types open Chord Lab with that voicing selected: Triads, Close Triads, Open Triads, Drop 2, Drop 3, Drop 2+4 and Shell Voicings. Half Diminished opens Chord Lab too.
- Upper structures, polychords and stacking chords open Structure Lab.
- Slash voicings, altered dominants and synonyms open Chord Architect.
- Voice leading opens Progression Lab.
- The Protean Chord opens Harmonic Universe.
Terms inside the apps
Free
In Chord Lab, Chord Architect, Diatonic Key Builder and Progression Lab, terms with a dotted underline carry a short definition:
- On a computer, hover over the term. Move onto the box to keep it open.
- On a phone or tablet, tap the term. Tap it again, or anywhere else, to close it.
Each box ends with Full entry in the Glossary →, which opens the full entry in a new tab so you don’t lose your place in the app.
You’ll find these on, for example, the voicing name under the chord in Chord Lab, the chord-family tabs in Chord Architect, the scale and mode names in Key Builder, and Voice Leading and Tritone Sub in Progression Lab.
Searching from the Help page
Free
The search box at the top of the Help page searches the Glossary along with every app guide. Glossary results are labelled Theory Glossary, and choosing one opens the Glossary at that entry.
On a phone
On a narrow screen each entry stacks, name above definition, and the search box runs the full width of the screen.
Works with
The Glossary links into:
- Chord Lab: the voicing type entries
- Chord Architect: slash voicings, altered dominants, synonyms
- Structure Lab: upper structures, polychords, stacking chords Pro
- Progression Lab: voice leading Pro
- Harmonic Universe: the Protean chord
Its definitions appear inside Chord Lab, Chord Architect, Diatonic Key Builder and Progression Lab, and in the Help page search. Each Player Project unit also links to the Glossary entry it relies on, such as Time signature, Cadence, Modal interchange and Drop 2.
Try it
Search for ø7, then altered, then pedal. Follow the Protean Chord entry into Harmonic Universe and find Bø7 in C major: its four synonyms orbit beside it.
