Chord analyser
Select any notes on the fretboard and the tool will suggest chord names that match what you have picked. Useful for checking a voicing, understanding a shape, or naming a chord you found by ear.
Chord Theory Fretboard
Voicing: -
Select a 7th first to use Upper Extended chords (9, 11, 13).
Chord: -
Root
3rds
5ths
7ths
Add / Extended
FAQ: What do the labels mean? Understanding chord names.
Chord labels can look complicated at first, but they are just a compact way of describing which notes are in the chord. The tool uses these labels because they are the common language musicians use to describe harmony.
Before you go any further, one important point: chord names only make sense once you understand intervals. Every chord is defined by the distances between notes, and the label is simply a shorthand for those distances. Read more below to find out more.
1What is a root?
Every chord starts from a root note.
The root is the note the chord is named after, and it acts as the reference point for everything else in the chord. When you see a chord label like C, Am, or G7, the letter at the beginning tells you the root.
For example:
- A C chord has C as its root
- An E♭ chord has E♭ as its root
Important clarification:
The root is not defined by pitch height or voicing. It doesn’t matter whether the root is the lowest note you play or where it appears on your instrument. The root is a theoretical reference, not necessarily the bass note.
All other notes in a chord are described by their intervallic distance from the root.
2What Are Intervals?
If the root is the starting point, an interval is the distance from that note to another note. Think of it as a measurement, like inches or centimetres, but for sound. In music, we describe this distance using two pieces of information: a distance (number) and a quality.
The Distance
The distance, formally called the interval number, tells us how far apart two notes are in terms of letter names.
To find it, start on the root and count up through the musical alphabet until you reach the second note. Include both notes in your count.
For example:
| From | Letter count | Interval |
|---|---|---|
| C to D | C–D | 2nd |
| C to E | C–D–E | 3rd |
| C to F | C–D–E–F | 4th |
This counting is alphabetical, so sharps and flats do not change the interval number.
| Example | Still a | Because it spans |
|---|---|---|
| C to E♭ | 3rd | C to E |
| C to F♯ | 4th | C to F |
At this stage, we only care about the letter distance, not the exact number of semitones.
The Quality
Once we know the distance (number), we also describe the interval’s quality. Quality tells us the exact size in semitones.
| Quality | Description |
|---|---|
| Perfect | Stable-sounding; used for unison, 4ths, 5ths, and octaves |
| Major | Brighter-sounding; used for 2nds, 3rds, 6ths, and 7ths |
| Minor | Darker-sounding; one semitone smaller than the major version |
| Augmented | One semitone larger than a perfect or major interval; adds tension |
| Diminished | One semitone smaller than a perfect or minor interval; adds tension |
Only 2nds, 3rds, 6ths, and 7ths can be major or minor.
Unison, 4th, 5th, and octave belong to the perfect group.
How Intervals Change
After learning interval number and quality, it helps to know how intervals change when we raise or lower them by semitones:
- If you take a perfect interval and raise it by one semitone, it becomes augmented.
- If you take a perfect interval and lower it by one semitone, it becomes diminished.
- If you take a major 2nd, 3rd, 6th, or 7th and lower it by one semitone, it becomes minor.
- If you take a minor 2nd, 3rd, 6th, or 7th and raise it by one semitone, it becomes major.
Intervals can also be raised or lowered by two semitones, creating more extreme augmented or diminished versions. For now, understanding the one-semitone changes above is enough.
3C Chromatic Reference (from root C)
In the previous section, we learned that an interval is the measured distance between two notes, and that in the context of chords these distances are described relative to the root note.
This section shows the next step: every possible interval you can form from a single reference note.
We use the chromatic scale because it contains all 12 pitches in the standard 12-tone system. That allows us to map:
- every semitone distance from the root
- the interval label for that distance
- the note name you land on
C Chromatic Scale (intervals from C)
Treat C as 1 (0 semitones). Moving to the right, each step rises by one semitone, showing how each pitch is named relative to the root.
Intervals
1
♭2
2
♭3
3
4
♯4 / ♭5
5
♭6
6
♭7
7
Semitones
0
1
2
3
4
5
6
7
8
9
10
11
Notes
C
C♯
D
D♯
E
F
F♯
G
G♯
A
A♯
B
This is the complete set of interval possibilities available from a root within the standard 12-tone system, excluding double flats and double sharps.
Chromatic Interval Names (relative to C)
| Interval | Name |
|---|---|
| 1 | Root / Tonic |
| ♭2 | Minor 2nd |
| 2 | Major 2nd |
| ♭3 | Minor 3rd |
| 3 | Major 3rd |
| 4 | Perfect 4th |
| Interval | Name |
|---|---|
| ♯4 / ♭5 | Augmented 4th / Diminished 5th |
| 5 | Perfect 5th |
| ♭6 | Minor 6th |
| 6 | Major 6th |
| ♭7 | Minor 7th |
| 7 | Major 7th |
C Major Scale Reference
For comparison, here is the C major scale, which selects seven of those twelve possible intervals.
C Major Scale (intervals from C)
Intervals
1
2
3
4
5
6
7
Notes
C
D
E
F
G
A
B
The chromatic scale shows all possible interval options.
The major scale shows which of those intervals the major scale uses.
4Let’s make our first chord! Triads explained
Now that we understand how intervals are named, we can begin looking at what combination of intervals make which chords.
The most basic type of chord we can make is called a triad. A triad is a chord made of three notes: a root, a third above the root, and a fifth above the root.
Triads are built using a system called tertian harmony, which simply means we make chords by stacking thirds. Stacking thirds means starting from a note and then adding the note a third above it, and then another third above that. Each note is still understood in relation to the original root.
Example in C major
C major triad:
Degrees
1
3
5
Notes
C
E
G
C major scale:
Degrees
1
2
3
4
5
6
7
Notes
C
D
E
F
G
A
B
Pick 1-3-5 from the scale.
The above is an example of a major triad. The intervals are the same for all major triads regardless of the root.
Example in C minor
C minor triad:
Degrees
1
♭3
5
Notes
C
E♭
G
C minor scale:
Degrees
1
2
♭3
4
5
♭6
♭7
Notes
C
D
E♭
F
G
A♭
B♭
Pick 1-♭3-5 from the scale.
All six triad types
The six triads below are the base chord formulas we use to build everything else.
Major triad
Degrees
1
3
5
Example
C
E
G
Minor triad
Degrees
1
♭3
5
Example
C
E♭
G
Diminished triad
Degrees
1
♭3
♭5
Example
C
E♭
G♭
Augmented triad
Degrees
1
3
♯5
Example
C
E
G♯
Sus2 triad
Degrees
1
2
5
Example
C
D
G
Sus4 triad
Degrees
1
4
5
Example
C
F
G
5Seventh Chords
Stacked thirds revisited
Earlier, we saw that triads are built by stacking thirds. This means starting from a root, adding a note a third above it, and then adding another third above that.
We can continue this same process. If we stack one more third on top of a triad, we get a seventh chord. Seventh chords add a new note that is a seventh above the root, creating a richer sound than a basic triad.
C major scale
To see this visually, here is the C major scale again:
Degrees
1
2
3
4
5
6
7
Notes
C
D
E
F
G
A
B
For a major 7th chord, take 1-3-5-7.
Creating seventh chords
If you remember from the interval section, the 2nd, 3rd, 6th, and 7th can be major or minor. This means the 7th above a root can either be:
- Major 7th (7) - a plain 7 in interval numbering
- Minor 7th (♭7) - one semitone lower than the major 7th
* We also technically have a bb7. This is a special edge case used with diminished triads, and we will explain it further down. For now, disregard it.
What this means is we can take any of our base triads and create combinations of triads with either of the 7th intervals. These give us unique chord types.
Seventh chord = Triad + 7 or Triad + ♭7
By combining a triad with either a major 7th or a minor 7th, we get different 7th chord variants.
Major/minor triad + 7th combinations
Using C as the root, below are the four base 7th-chord combinations: a major triad + 7, a major triad + ♭7, a minor triad + ♭7, and a minor triad + 7.
Major 7th (maj7)
Degrees
1
3
5
7
Example
C
E
G
B
Dominant 7th (7)
Degrees
1
3
5
♭7
Example
C
E
G
B♭
Minor 7th (m7)
Degrees
1
♭3
5
♭7
Example
C
E♭
G
B♭
Minor-major 7th (mMaj7)
Degrees
1
♭3
5
7
Example
C
E♭
G
B
Other less common 7th chords
There are other less commonly used 7th chords. These are made by taking other triad types (suspended, augmented, diminished, or altered-fifth variants) and adding either a major 7th (7) or a minor 7th (♭7).
These chords are less frequently used but add colour and tension to music.
Formulas for less common 7th chords:
Half-diminished 7th (m7♭5)
Degrees
1
♭3
♭5
♭7
Example
C
E♭
G♭
B♭
Dominant 7th flat 5 (7♭5)
Degrees
1
3
♭5
♭7
Example
C
E
G♭
B♭
Diminished-major 7th (dimMaj7)
Degrees
1
♭3
♭5
7
Example
C
E♭
G♭
B
Minor 7th sharp 5 (m7♯5)
Degrees
1
♭3
♯5
♭7
Example
C
E♭
G♯
B♭
Suspended 2nd 7th (sus2 7)
Degrees
1
2
5
♭7
Example
C
D
G
B♭
Suspended 4th 7th (sus4 7)
Degrees
1
4
5
♭7
Example
C
F
G
B♭
Augmented 7th (aug7)
Degrees
1
3
♯5
♭7
Example
C
E
G♯
B♭
Augmented-major 7th (augMaj7)
Degrees
1
3
♯5
7
Example
C
E
G♯
B
Fully Diminished 7th Chord
The fully diminished 7th chord is the most tense and dissonant 7th chord. It is built from a diminished triad with a diminished 7th on top.
Structure
- Diminished triad: 1 - ♭3 - ♭5
- Add diminished 7th: ♭♭7
- Full formula: 1 - ♭3 - ♭5 - ♭♭7
- C example: C - E♭ - G♭ - B♭♭ (A)
Fully diminished 7th (dim7)
Degrees
1
♭3
♭5
♭♭7
Example
C
E♭
G♭
B♭♭
Why we use a ♭♭7
The double flat looks odd at first, but it is just a naming rule so the chord stays consistent.
A diminished 7th chord is built by stacking minor thirds on top of a diminished triad. If we measure the top note from the root:
- A minor 7th (♭7) is 10 semitones above the root.
- A diminished 7th is one semitone smaller, so it is 9 semitones above the root.
That top note is still functioning as “the 7th” of the chord, so we keep the number 7 in the label. Writing it as ♭♭7 tells you it is a seventh that has been lowered twice, rather than switching to a different interval name.
It also keeps the chord’s shape consistent on paper, because every step stays a minor third:
- C to E♭ is a minor third
- E♭ to G♭ is a minor third
- G♭ to B♭♭ is a minor third
One extra thing that helps: on a guitar (and a piano), B♭♭ sounds the same as A. But we still write B♭♭ because it shows the chord is built as stacked thirds, and that is what makes diminished 7th chords sound tense and symmetrical.
6Extended Chords (9ths, 11ths, 13ths)
We’ve already seen that triads are built by stacking two thirds: root → third → fifth.
Seventh chords extend this idea by adding one more third on top of the triad.
Extended chords are the next step in the same process: we keep stacking thirds above the seventh to add more notes.
If we continue this stacking, we get the sequence: 1-3-5-7-9-11-13.
This shows that the principle is the same at every level: triads → seventh chords → extended chords.
When we add notes beyond the seventh, the numbers 9, 11, and 13 can seem confusing at first.
The key is to remember Section 2: intervals are counted alphabetically from the root.
- A 9th is the 2nd above the octave.
- An 11th is the 4th above the octave.
- A 13th is the 6th above the octave.
So extended chord numbers are not arbitrary. They are the next stacked intervals above the seventh, following the same counting system.
C Major Example - Two Octaves
Degree
1
2
3
4
5
6
7
Note
C
D
E
F
G
A
B
Degree
8
9
10
11
12
13
14
Note
C
D
E
F
G
A
B
Altered Notes in Extended Chords
Extended chords can include notes that are raised (♯) or lowered (♭).
- The alteration applies only to that specific interval.
- It does not change the overall type of the chord.
If we alter one upper note, we usually notate that interval as altered rather than renaming the chord completely. This adds colour or tension while keeping the base structure.
Required Intervals in Extended Chords
When building extended chords, each new note depends on the notes that come before it.
- Extensions are stacked on top of the existing chord.
- You cannot have a 9th without root, third, fifth, and seventh implied.
- An 11th also requires the earlier intervals to be implied, and the same applies for higher extensions.
In practice, some notes may be omitted, but the chord is still understood to include the underlying structure.
Practical Limitations on Guitar
Playing every note in extended chords on guitar is often impossible. We have four fingers and one thumb, and only six strings, so there is a limit to how many notes can fit in one voicing.
Because of this, non-vital intervals are often left out. For example, in an 11th chord a guitarist may keep the root, third, seventh, and 11th, while omitting notes like the fifth or 9th to make the shape playable.
7Add chords and 6th chords
Add chords are a simple way to get a richer sound without moving into full extended harmony. The idea is: start with a normal major or minor triad, then add one extra note. Importantly, you keep the third in place, so the chord still clearly sounds major or minor.
That same concept includes 6th chords, which are essentially "add6" chords in practice.
What "add" means
Begin with a triad:
- Major triad: 1 3 5
- Minor triad: 1 ♭3 5
Then add one extra scale degree:
- add9: 1 3 5 9 (or 1 ♭3 5 9)
- add11: 1 3 5 11 (or 1 ♭3 5 11)
- add13: 1 3 5 13 (or 1 ♭3 5 13)
Where 6th chords fit
A 6th chord is a triad plus a 6th:
- 6: 1 3 5 6
- m6: 1 ♭3 5 6
You will sometimes see the name "add6", but most guitarists and theory resources just call it "6" or "m6". The important part for this tool is the structure: it is still a triad with one added note, and no 7th implied.
6th chords vs 13th chords
This is the same "same note, different meaning" problem as add9 vs 9:
- A 6th chord does not imply a 7th.
- A 13th chord usually implies a 7th (and is treated as an extended chord).
So:
- C6 is C E G plus A.
- C13 is a dominant-type extension and typically implies B♭ (the 7th) as part of the chord structure, even if it is not always voiced.
Add9 vs add2 (and add11 vs add4)
On paper, 2 and 9 are the same note in different octaves. The same is true for 4 and 11, and for 6 and 13.
In real guitar voicings, the "add9" label is often used even if the added note is close to the triad, because it describes the colour more than the exact octave.
Add chords vs extended chords
A practical rule:
- Add chords (including 6th chords) are triads with an extra note, and do not include a 7th by default.
- Extended chords (9, 11, 13) usually imply a 7th as part of the chord.
Add chords vs suspended chords
Suspended chords replace the third, add chords keep it:
- Csus2 is 1 2 5 (no 3rd).
- Cadd9 is 1 3 5 plus 9 (3rd stays).
That is why add chords feel like a normal major or minor chord with extra sparkle, while sus chords feel more open and unresolved.
FAQ: I can’t find this chord? Limitations of the tool.
Short Answer
If a chord does not appear, it usually means the tool filtered it out for playability or naming rules, not that the chord is impossible in every context.
- not every enharmonic equivalent is currently listed as its own option
- most slash chords and inversions are intentionally not included
How I built it
When I first built the voicing system, I did it in two parts. I manually coded a library of standard movable shapes for triads and 7th chords, then I let the engine generate additional voicings from those foundations. On paper that sounds ideal: cover the common shapes, then expand outward.
Where it broke down
In reality it caused a tonne of issues. The fretboard can produce a huge number of technically valid note combinations, and once you start generating variations, a lot of them become physically impossible to fret, awkward to mute cleanly, or just musically unhelpful on guitar.
Why the filters exist
So the engine needed another layer of rules, not theory rules, but hand realism rules, to stop it outputting shapes that look correct but would never be used in practice.
That is why this page uses two layers of logic: music theory, and playability filtering. The goal is to keep results useful and inspiring without burying you in unusable shapes, and it is always a balancing act between being theoretically thorough and staying practically playable.
1Why voicing filters exist
When I started generating voicings, I quickly realised theory alone doesn’t get you to usable results. The fretboard can produce an insane number of technically valid note combinations, but most of them are either physically unrealistic or musically pointless on guitar. So I had to introduce an entire second set of rules that have nothing to do with chord formulas and everything to do with what a hand can actually do.
That meant deciding things like:
- how wide a fret stretch is still reasonable before a voicing stops being useful
- which strings a voicing is allowed to live on, and when muting strings is acceptable
- whether a shape is realistically barre-able, and how dense a grip can be before it becomes a circus trick
- when it’s OK to omit notes or double notes so the voicing stays playable while still sounding like the chord
2The filtering tradeoff
The tricky part is those rules are all judgement calls. If I try to output every valid voicing, it becomes unusable immediately because the user is buried in nonsense. If I filter too hard, the tool looks broken because people assume missing shapes are an error rather than a deliberate choice.
So I’m constantly aiming for the middle ground: enough variety that the results feel inspiring, but filtered enough that every suggestion feels like something a guitarist would actually play.
3Root vs bass in chord naming
On my page I’m explicit about something that confuses people early on: the root is a theoretical reference, not necessarily the lowest note you play. In other words, the bass note does not automatically define the chord name.
But in a chord tool, that creates a cascade of decisions:
- Do you assume the chosen “root” control is authoritative, even if the selected notes suggest a different root?
- Do you allow “rootless” voicings to still resolve to a chord name?
- Do you treat the bass note as a hint, or ignore it to avoid misleading labels?
Every option is defensible. Each one also creates edge cases that users will call “bugs” if they expected a different convention.
4What I allow theory-wise vs what I force
I do not treat all chord tones equally. Some tones define the quality, others are negotiable when guitar reality gets in the way.
- For plain triads and plain 7th chords, I keep all defining tones mandatory.
- For add/extended families, I still force the root and quality-defining tones (major/minor/sus and required altered fifths).
- The perfect 5th can be omitted in many extended cases, but not in structures where that 5th quality is part of the identity (like m7b5, 7b5, m7#5, diminished, and augmented families).
- If the chord family implies a 7th (7/9/11/13 style names), that 7th still has to be present.
So yes, omissions are allowed, but only in places where they preserve the musical function instead of changing the chord into something else.
5Extension triage: what survives when space runs out
When an extended chord has too many colour tones, I prioritise families rather than trying to cram everything in.
- 13-family chords keep the upper colour priority, while 9/11 can become optional.
- 11-family chords are handled carefully so natural 11 against a major 3rd does not dominate by default.
- 9-family chords still choose a specific colour (for example b9/#9/9) instead of pretending all variants are equally practical in one grip.
This is deliberate triage, not a math bug: one good identity read beats a crowded, unreadable shape.
6Physical rules I enforce by default
Even after the theory checks pass, I still have to decide what should appear as a default suggestion, because the fretboard can generate endless “valid” shapes that are not sensible to play.
This part is less about harmony and more about what a guitarist will realistically reach for.
The questions behind the filters are basically:
- is this stretch reasonable for most hands, most of the time?
- does this shape rely on an awkward partial barre or grip that only works as a one-off stunt?
- does it skip strings in a way that makes it feel more like a puzzle than a chord you would actually use?
- does it require so much squeezing and muting that it will fall apart the moment you try to change chords?
None of those are universal rules. They are judgement calls. But without them, the results become a dump of possibilities rather than useful suggestions.
7Why a theoretically valid voicing still gets rejected
Even after interval checks, a voicing can still fail if it breaks positional constraints built into this tool.
- Voicings must include at least three played notes and all required identity tones.
- I enforce root-position output in the voicing engine: the lowest played note must be the root, anchored on strings 6/5/4.
- For template-derived shapes, the expected root string anchor is also enforced.
That means some inversions and edge-case grips are intentionally excluded, even if they exist on paper.
8Fallback behaviour when nothing passes
If no playable option survives for a dense/altered set, I do a controlled reduction pass instead of returning garbage or silence.
I drop less-critical colour tones step by step, while protecting core identity tones (root, quality-defining third/sus logic, altered-fifth identity, and implied seventh when required) until at least one practical voicing appears.
So if you see a leaner result than expected, it is usually the tool choosing a playable approximation over an impossible literal stack.
9How the analyser picks one label when several fit
Analyser naming is ranking, not absolute truth. For simple sets it favours exact interval fits; for denser sets it leans more on bass-aware interpretations.
- Add-family labels are deprioritised when a 7th is already present.
- Conflicting quality reads (like sus labels with explicit 3rds) are penalized.
- If only the 5th is missing, shell labels can still resolve with a
-5suffix. - Enharmonic alternatives are shown when the respelling is genuinely useful.
So when users disagree with a label, they are often seeing a different ranking philosophy, not a broken parser.