Complete guide to the chord system in Strumboli

Chords & Progressions

Strumboli includes a comprehensive chord system with built-in progressions and flexible chord notation. This guide covers everything from basic chord types to creating custom progressions.

Chord Notation

Supported Chord Types

Triads (3-note chords)

Notation	Name	Intervals	Example	Notes (Octave 4)
`maj` or (none)	Major	0, 4, 7	`C` or `Cmaj`	C4, E4, G4
`m` or `min`	Minor	0, 3, 7	`Cm` or `Cmin`	C4, Eb4, G4
`dim`	Diminished	0, 3, 6	`Cdim`	C4, Eb4, Gb4
`aug`	Augmented	0, 4, 8	`Caug`	C4, E4, G#4
`sus2`	Suspended 2nd	0, 2, 7	`Csus2`	C4, D4, G4
`sus4`	Suspended 4th	0, 5, 7	`Csus4`	C4, F4, G4
`5`	Power chord	0, 7	`C5`	C4, G4

Seventh Chords (4-note chords)

Notation	Name	Intervals	Example	Notes (Octave 4)
`7`	Dominant 7th	0, 4, 7, 10	`C7`	C4, E4, G4, Bb4
`maj7`	Major 7th	0, 4, 7, 11	`Cmaj7`	C4, E4, G4, B4
`m7` or `min7`	Minor 7th	0, 3, 7, 10	`Cm7`	C4, Eb4, G4, Bb4
`dim7`	Diminished 7th	0, 3, 6, 9	`Cdim7`	C4, Eb4, Gb4, A4
`aug7`	Augmented 7th	0, 4, 8, 10	`Caug7`	C4, E4, G#4, Bb4

Extended Chords (5+ notes)

Notation	Name	Intervals	Example	Notes (Octave 4-5)
`9`	Dominant 9th	0, 4, 7, 10, 14	`C9`	C4, E4, G4, Bb4, D5
`maj9`	Major 9th	0, 4, 7, 11, 14	`Cmaj9`	C4, E4, G4, B4, D5
`m9` or `min9`	Minor 9th	0, 3, 7, 10, 14	`Cm9`	C4, Eb4, G4, Bb4, D5
`add9`	Major add 9	0, 4, 7, 14	`Cadd9`	C4, E4, G4, D5
`6`	Major 6th	0, 4, 7, 9	`C6`	C4, E4, G4, A4
`m6` or `min6`	Minor 6th	0, 3, 7, 9	`Cm6`	C4, Eb4, G4, A4

Root Notes

All 12 chromatic notes are supported:

Sharp notation: C, C#, D, D#, E, F, F#, G, G#, A, A#, B

Flat notation: C, Db, D, Eb, E, F, Gb, G, Ab, A, Bb, B

Both notations produce identical results (e.g., C# = Db).

Octave Range

When using chord notation with actions, you can specify octave 0-9. Default is octave 4 (middle C).

Using Chords

In Button Actions

Use set-strum-chord action:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "C"],        // C major, octave 4
    "2": ["set-strum-chord", "Am7", 3],   // A minor 7th, octave 3
    "3": ["set-strum-chord", "G9", 2]     // G dominant 9th, octave 2
  }
}

Examples by Style

Pop/Rock:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "C"],
    "2": ["set-strum-chord", "G"],
    "3": ["set-strum-chord", "Am"],
    "4": ["set-strum-chord", "F"]
  }
}

Jazz:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "Cmaj7"],
    "2": ["set-strum-chord", "Dm7"],
    "3": ["set-strum-chord", "G7"],
    "4": ["set-strum-chord", "Cmaj9"]
  }
}

Blues:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "E7"],
    "2": ["set-strum-chord", "A7"],
    "3": ["set-strum-chord", "B7"]
  }
}

Rock/Metal Power Chords:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "E5", 2],
    "2": ["set-strum-chord", "G5", 2],
    "3": ["set-strum-chord", "A5", 2],
    "4": ["set-strum-chord", "C5", 2]
  }
}

Chord Progression Presets

Chord progressions are pre-configured sets of chords that automatically fill all 8 tablet buttons. They're perfect for playing in a specific key or style.

How Progressions Work

When you set tabletButtons to a progression name:

{
  "tabletButtons": "c-major-pop"
}

It expands to individual button actions:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "C"],
    "2": ["set-strum-chord", "G"],
    "3": ["set-strum-chord", "Am"],
    "4": ["set-strum-chord", "F"],
    "5": ["set-strum-chord", "C"],    // Wraps back to start
    "6": ["set-strum-chord", "G"],
    "7": ["set-strum-chord", "Am"],
    "8": ["set-strum-chord", "F"]
  }
}

Wrapping: If a progression has fewer chords than buttons (8), it repeats from the beginning to fill all buttons.

Major Key Progressions

C Major

Preset	Chords	Description
`c-major-basic`	C, F, G, Am	Classic I-IV-V-vi
`c-major-pop`	C, G, Am, F	Popular I-V-vi-IV
`c-major-jazz`	Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, Bm7	Diatonic 7th chords

G Major

Preset	Chords	Description
`g-major-basic`	G, C, D, Em	Classic I-IV-V-vi
`g-major-pop`	G, D, Em, C	Popular I-V-vi-IV
`g-major-jazz`	Gmaj7, Am7, Bm7, Cmaj7, D7, Em7, F#m7	Diatonic 7th chords

D Major

Preset	Chords	Description
`d-major-basic`	D, G, A, Bm	Classic I-IV-V-vi
`d-major-pop`	D, A, Bm, G	Popular I-V-vi-IV
`d-major-jazz`	Dmaj7, Em7, F#m7, Gmaj7, A7, Bm7, C#m7	Diatonic 7th chords

A Major

Preset	Chords	Description
`a-major-basic`	A, D, E, F#m	Classic I-IV-V-vi
`a-major-pop`	A, E, F#m, D	Popular I-V-vi-IV

E Major

Preset	Chords	Description
`e-major-basic`	E, A, B, C#m	Classic I-IV-V-vi
`e-major-pop`	E, B, C#m, A	Popular I-V-vi-IV

F Major

Preset	Chords	Description
`f-major-basic`	F, Bb, C, Dm	Classic I-IV-V-vi
`f-major-pop`	F, C, Dm, Bb	Popular I-V-vi-IV

Minor Key Progressions

A Minor

Preset	Chords	Description
`a-minor-basic`	Am, Dm, Em, F, E	Classic i-iv-v
`a-minor-pop`	Am, F, C, G, E	Popular minor progression
`a-minor-sad`	Am, Em, F, C, G, Dm, E	Melancholic 7-chord progression

E Minor

Preset	Chords	Description
`e-minor-basic`	Em, Am, Bm, C, B	Classic i-iv-v
`e-minor-pop`	Em, C, G, D, B	Popular minor progression

D Minor

Preset	Chords	Description
`d-minor-basic`	Dm, Gm, Am, Bb, A	Classic i-iv-v
`d-minor-pop`	Dm, Bb, F, C, A	Popular minor progression

Blues Progressions

Preset	Chords	Description
`blues-e`	E7, A7, B7	12-bar blues in E
`blues-a`	A7, D7, E7	12-bar blues in A
`blues-g`	G7, C7, D7	12-bar blues in G

Rock Progressions

Preset	Chords	Description
`rock-classic`	E, A, D, B	Classic rock changes
`rock-power`	E5, G5, A5, C5, D5	Power chord progression

Jazz Progressions

Preset	Chords	Description
`jazz-251-c`	Dm7, G7, Cmaj7, Em7, A7	ii-V-I in C major
`jazz-251-f`	Gm7, C7, Fmaj7, Am7, D7	ii-V-I in F major

Gospel Progressions

Preset	Chords	Description
`gospel-c`	C, Am7, Dm7, G7, F	Gospel in C
`gospel-g`	G, Em7, Am7, D7, C	Gospel in G

Note Spread

When you set a chord, Strumboli automatically adds octaves above and below based on your strumming configuration:

{
  "strumming": {
    "initialNotes": ["C4", "E4", "G4"],
    "upperNoteSpread": 3,
    "lowerNoteSpread": 3
  }
}

With these settings, setting a C major chord (C4, E4, G4) creates:

Lower spread (3 notes):

C3, E3, G3

Core chord:

C4, E4, G4

Upper spread (3 notes):

C5, E5, G5

Total: 9 notes to strum through

Adjusting Note Spread

Wide spread (more notes):

{
  "strumming": {
    "upperNoteSpread": 5,
    "lowerNoteSpread": 5
  }
}

Creates a fuller, richer sound with more notes.

Narrow spread (fewer notes):

{
  "strumming": {
    "upperNoteSpread": 1,
    "lowerNoteSpread": 1
  }
}

More focused, easier to control.

Asymmetric spread:

{
  "strumming": {
    "upperNoteSpread": 4,
    "lowerNoteSpread": 1
  }
}

Emphasizes higher octaves.

No spread (chord only):

{
  "strumming": {
    "upperNoteSpread": 0,
    "lowerNoteSpread": 0
  }
}

Only the core chord notes.

Custom Progressions

You can create your own chord progressions by editing /server/chord_progressions.json.

File Structure

{
  "category-name": {
    "progression-name": ["Chord1", "Chord2", "Chord3", ...]
  }
}

Adding a Custom Progression

Open /server/chord_progressions.json and add your progression:

{
  "major": {
    "c-major-basic": ["C", "F", "G", "Am"],
    "my-custom-c": ["C", "Em", "F", "G"]
  },
  "custom": {
    "my-favorite": ["Cmaj7", "Fmaj7", "Dm7", "G7", "Am7"],
    "experimental": ["Cmaj9", "Eb7", "Abmaj7", "Dbmaj7"]
  }
}

Then use it:

{
  "tabletButtons": "my-custom-c"
}

Progression Best Practices

Length: Any length works (3-8 chords is typical)
- Short (3-4): Repeats more often, good for loops
- Long (5-7): More variety before repeating
Naming: Use lowercase with hyphens
- ✅ my-custom-progression
- ❌ My Custom Progression
Avoid duplicates: Don't repeat chords in the same progression
- The wrap-around feature handles repetition automatically
Categories: Organize by style or key
- major, minor, blues, jazz, rock, gospel, custom

Example: Creating a Progression Collection

{
  "my-songs": {
    "verse-a": ["C", "G", "Am", "F"],
    "chorus-a": ["F", "C", "G", "Am"],
    "bridge-a": ["Dm", "G", "C", "Am"],
    "outro-a": ["F", "G", "C"]
  }
}

Use in settings:

{
  "tabletButtons": "verse-a"
}

Switch progressions by changing settings and restarting, or use buttons with set-chord-in-progression to access different progressions dynamically.

Progression Performance Techniques

Technique 1: Static Progression (Preset)

Use a preset for a consistent key:

{
  "tabletButtons": "c-major-pop"
}

Best for:

Single-key songs
Practice and learning
Simple performances

Technique 2: Dynamic Progression (Increment Actions)

Use buttons to navigate through a progression:

{
  "stylusButtons": {
    "primaryButtonAction": ["increment-chord-in-progression", "c-major-pop"],
    "secondaryButtonAction": ["increment-chord-in-progression", "c-major-pop", -1]
  },
  "tabletButtons": {
    "1": ["set-chord-in-progression", "c-major-pop", 0],  // Reset to C
    "2": "toggle-repeater",
    "3": ["transpose", 12],
    "4": ["transpose", -12]
  }
}

Best for:

Sequential chord changes
Foot pedal control
Following song structure

Technique 3: Mixed Chords and Utilities

Combine specific chords with utility actions:

{
  "tabletButtons": {
    "1": ["set-strum-chord", "C"],
    "2": ["set-strum-chord", "G"],
    "3": ["set-strum-chord", "Am"],
    "4": ["set-strum-chord", "F"],
    "5": ["set-strum-chord", "Dm7"],
    "6": ["transpose", 12],
    "7": ["transpose", -12],
    "8": "toggle-repeater"
  }
}

Best for:

Custom song arrangements
Mixing common chords with special features
Performance flexibility

Technique 4: Multiple Progressions

Access different progressions for song sections:

{
  "tabletButtons": {
    "1": ["set-chord-in-progression", "c-major-pop", 0],      // Verse: C
    "2": ["set-chord-in-progression", "c-major-pop", 1],      // Verse: G
    "3": ["set-chord-in-progression", "c-major-pop", 2],      // Verse: Am
    "4": ["set-chord-in-progression", "c-major-pop", 3],      // Verse: F
    "5": ["set-chord-in-progression", "a-minor-sad", 0],      // Bridge: Am
    "6": ["set-chord-in-progression", "a-minor-sad", 1],      // Bridge: Em
    "7": ["increment-chord-in-progression", "c-major-pop"],   // Next
    "8": ["increment-chord-in-progression", "a-minor-sad"]    // Next (bridge)
  }
}

Best for:

Complex song structures
Switching between verse/chorus/bridge
Multi-section performances

Common Chord Progressions

Here are some classic progressions you can create:

Pop/Rock Standards

I-V-vi-IV (most popular):

C major: C, G, Am, F (c-major-pop)
G major: G, D, Em, C (g-major-pop)
D major: D, A, Bm, G (d-major-pop)

I-IV-V (classic rock):

C major: C, F, G (c-major-basic)
E major: E, A, B (e-major-basic)

Blues

12-bar blues (3-chord):

E blues: E7, A7, B7 (blues-e)
A blues: A7, D7, E7 (blues-a)

Jazz

ii-V-I (foundational):

C major: Dm7, G7, Cmaj7 (jazz-251-c)
F major: Gm7, C7, Fmaj7 (jazz-251-f)

Minor Keys

Natural minor (sad/emotional):

A minor: Am, F, C, G (a-minor-pop)
E minor: Em, C, G, D (e-minor-pop)

Tips for Working with Chords

Learning Chord Notation

Start with basic triads:

Major: C, G, F, D
Minor: Am, Em, Dm
Then add 7ths: Cmaj7, G7, Am7

Voicing Considerations

Lower octaves (1-3): Bass, foundations Middle octaves (3-5): Chords, melody Upper octaves (5-7): Leads, texture

Combining with Note Spread

Wide spread (5+ notes): Fuller chords, ambient
Narrow spread (1-2 notes): Focused, clear
Asymmetric spread: Emphasize range

Performance Tips

Practice progressions before performing
Mark buttons with tape/stickers for visual reference
Test octaves to find the right range for your sound
Combine with transpose for even more flexibility

Troubleshooting

Chord Sounds Wrong

Check octave: Too high or low octaves sound unusual
Verify notation: Ensure spelling is correct (case-sensitive)
Check spread: Very wide spreads can sound muddy

Progression Not Loading

Check name: Must match exactly (case-sensitive, use hyphens)
Verify file: Ensure chord_progressions.json is valid JSON
Restart: Changes to progressions require restarting Strumboli

Button Not Playing Chord

Verify button number: Must match your tablet (1-8 typically)
Check action format: Ensure proper array format
Look at console: Error messages will indicate the problem

Next Steps

Actions Reference - Full action documentation
Settings Reference - Complete settings guide
Configuration Overview - Understanding the config system
Getting Started - Installation and setup

Chord Reference Tables

Quick reference for copying into configurations:

Major Chords (All Keys)

C, D, E, F, G, A, B
C#/Db, D#/Eb, F#/Gb, G#/Ab, A#/Bb

Minor Chords (All Keys)

Cm, Dm, Em, Fm, Gm, Am, Bm
C#m/Dbm, D#m/Ebm, F#m/Gbm, G#m/Abm, A#m/Bbm

Common 7th Chords

Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, Bm7b5
C7, D7, E7, F7, G7, A7, B7

Power Chords

C5, D5, E5, F5, G5, A5, B5