Guitar Music Theory: The 19 Three-Note Pitch Class Sets
Understanding the foundations of music theory can transform your guitar playing. One of those foundations is the three-note pitch class set: the building block of triads, shell voicings and scale fragments. Pick any of the 19 sets below to see its shape on the pitch-class clock, hear it, transpose it and find it on the fretboard.
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What Are Three-Note Pitch Classes?
A pitch class is every note with the same name, in any octave. Every C on the guitar, from the 5th string, 3rd fret to the 1st string, 8th fret, is the same pitch class. A three-note pitch class set is any group of three different pitch classes, like C, E and G.
Lay the 12 notes around a clock and every three-note set becomes a triangle. Moving the triangle around the clock is transposition: C major becomes D♭ major, D major and so on, but the shape never changes. That’s why the shape, not the note names, tells you what kind of sound you have.
Why There Are Exactly 19
There are 220 ways to choose three notes out of twelve. Group together every set that’s just a transposition of another and you’re left with exactly 19 unique shapes. Every three-note chord or melody fragment you’ll ever play is one of them.
Music theorists often go one step further and also treat a set and its mirror image (its inversion) as the same. Flip a major triad upside down and you get a minor triad, so major and minor become one family. Counted that way, the 19 shrink to 12 families. Switch the tool to “Mirror families” to see the pairs, or tap “Show mirror” on the clock.
The 19 Three-Note Pitch Class Sets
| Set | On C | Mirror partner |
|---|---|---|
| Major triad (1-3-5) | C E G | Minor triad |
| Minor triad (1-♭3-5) | C E♭ G | Major triad |
| Diminished triad (1-♭3-♭5) | C E♭ G♭ | Itself |
| Augmented triad (1-3-♯5) | C E G♯ | Itself |
| Suspended 4th (1-4-5) | C F G | Itself |
| Suspended ♭2 (1-♭2-5) | C D♭ G | Suspended ♯4 |
| Suspended ♯4 (1-♯4-5) | C F♯ G | Suspended ♭2 |
| Major 7 no 5 (1-3-7) | C E B | 1-3-4 |
| Minor 7 no 5 (1-♭3-♭7) | C E♭ B♭ | 1-♭3-4 |
| Dominant 7 no 5 (1-3-♭7) | C E B♭ | 1-3-♯4 |
| 1-3-4 (major scale) | C E F | Major 7 no 5 |
| 1-♭3-4 (minor scale) | C E♭ F | Minor 7 no 5 |
| 1-3-♯4 (Lydian) | C E F♯ | Dominant 7 no 5 |
| 1-2-3 (major scale) | C D E | Itself |
| 1-2-♭3 (minor scale) | C D E♭ | 1-♭2-♭3 |
| 1-♭2-♭3 (Phrygian) | C D♭ E♭ | 1-2-♭3 |
| 1-♭2-2 (chromatic) | C D♭ D | Itself |
| 1-♭2-3 (Phrygian dominant) | C D♭ E | 1-♭3-3 |
| 1-♭3-3 (blues) | C E♭ E | 1-♭2-3 |
Some pairs are surprising. A major 7th shell (C E B) and the 1-3-4 fragment (C E F) don’t look related, but on the clock one is the other flipped over. Try it in the tool.
Applying Three-Note Pitch Classes to Guitar
On guitar, any three-note set can be played on three adjacent strings. The tool finds a compact shape on each string set, so you can hear how the same set sounds in different registers. Some examples:
- Major triad (C E G): open position, barre chords or small three-string triads anywhere on the neck.
- Minor triad (A C E): open A minor or movable shapes.
- Diminished triad (B D F): a passing chord that builds tension.
- Dominant 7 no 5 (G B F): the classic jazz and blues shell voicing.
Practicing these sets across the fretboard builds a deeper understanding of chord construction and voice leading. Use the fretboard map to see every place the three notes live, and switch between degrees and note names.
Why This Matters for Guitarists
- Improvisation: recognize chord tones and target them in your solos.
- Composition: build progressions and melodies with intentional harmonic color.
- Harmony: analyze songs and hear what’s underneath the chord symbols.
Knowing that there are only 19 shapes turns the fretboard from a sea of notes into a short list of patterns you can learn, hear and use.
Pitch Class FAQ
What is the difference between a pitch and a pitch class?
A pitch is one specific note, like middle C. A pitch class is all the C’s in every octave together. Pitch class sets ignore octave and order, so C E G, E G C and a spread-out C major chord are all the same set.
What is a Forte number?
Allen Forte catalogued every pitch class set. Three-note sets are numbered 3-1 to 3-12, one per mirror family. “A” and “B” mark the two mirror images in a pair, so the major triad is 3-11B and the minor triad is 3-11A.
What is prime form?
Prime form is a set written in its most compact version, starting on 0. Major and minor triads share the prime form (0 3 7), because they belong to the same mirror family.
Why are there only 4 augmented triads?
The augmented triad splits the octave into three equal major 3rds, so moving it up a major 3rd gives back the same notes. C augmented, E augmented and G♯ augmented all contain C, E and G♯.
Keep exploring with our chord calculator, the interactive circle of fifths and modes. For a full breakdown of scales, chords and theory, see our Guitar Music Theory Guide, or take guitar lessons at Canton Music Academy. Book online in 3 easy steps!
