Interactive Fretboard Tool

1Pitches and 12-tone equal temperament

Modern Western instruments use a system called 12-tone equal temperament.

This means an octave is divided into 12 evenly spaced notes. After the 12th note, the pattern repeats at a higher or lower pitch.

Those 12 notes are:

C  |  C# or Db  |  D  |  D# or Eb  |  E  |  F  |  F# or Gb  |  G  |  G# or Ab  |  A  |  A# or Bb  |  B

2Enharmonic equivalents

Sometimes, the same sounding note can be given two different names.

For example:

• C# and Db
• F# and Gb
• A# and Bb

These pairs sound identical, but they are labelled differently.

When two different note names refer to the same sounding note, they are called enharmonic equivalents. This term is most often used for single notes, but it can also be applied more broadly to other concepts such as chords that are spelled differently but sound the same.

312 sounding major keys vs 15 written major keys

Because there are only 12 possible sounding notes, there are only 12 distinct sounding major keys.

However, because some notes can be written in two different ways, some major keys can also be written in two different ways.

When we count major keys by how they are written in notation, the total becomes 15.

To understand why there are 15 and not more, we first need to understand how music is written a little.

4Basic notation: staff, accidentals, and key signatures

Music is usually written on a staff made of five lines and four spaces. These represent the letter names A to G repeating as you move up or down.

To show sharps and flats, we use accidentals:

• # raises a note
• b lowers a note
• ♮ cancels a sharp or flat

If we wrote these accidentals next to every note, the music would be cluttered and hard to read.

So instead, we use a key signature at the start of the music. The key signature tells you which notes are always sharp or flat in that key, so accidentals do not have to be written constantly.

5Why we choose sharps in some keys and flats in others

When writing a major scale, musicians try to keep the spelling clear and consistent.

A common rule of thumb is to avoid using the same letter name twice in a scale, such as F and F# in the same key. If we didn't, the music would become harder to read because the same line or space would represent two versions of the same letter.

This is one reason enharmonic spellings exist.

For example, the key we call Bb major:

Bb C D Eb F G A

This uses each letter once and has a simple key signature of two flats.

This key sounds the same as A# major. But if we try to write A# major while following the same rules, we are forced into:

A# B# C## D# E# F## G##

This introduces double sharps and makes the music far harder to read.

For this reason, we always use Bb major instead of A# major. This is also true for Eb major and Ab major.

The choice between sharps and flats is about keeping the key signature simple and the music readable.

6Where the number 15 comes from

If you list the major keys as they are correctly written in notation, you get:

C, G, D, A, E, B, F#, C#

F, Bb, Eb, Ab, Db, Gb, Cb

That is 15 correctly written major keys.

Three pairs sound the same but are written differently:

• C# major and Db major
• F# major and Gb major
• B major and Cb major

In practice, the version used depends on which spelling keeps the notation consistent with nearby keys and easiest to read.

7Relative minor keys

Every major key has a relative minor key that shares the same key signature.

For example:

• C major and A minor share no sharps or flats.
• G major and E minor share one sharp.
• F major and D minor share one flat.

This means:

• There are 12 distinct sounding major keys
• There are 12 distinct sounding minor keys

So in practice, there are 24 distinct sounding keys.

When counted by correct written spelling:

• There are 15 written major keys
• There are 15 written minor keys

So in theory, there are 30 written keys.

Final answer

• 12 major keys by sound, 15 by spelling
• 12 minor keys by sound, 15 by spelling
• 24 distinct sounding keys in practice
• 30 keys when counted by written notation

1Tonic

The tonic is the home note of a scale or key. It is the note everything is measured against, and it is where things tend to feel “resolved”.

Think of it as 1.

2Intervals

An interval is the distance between two notes.

When we talk about scales, we usually measure every note from the tonic (1). That gives us a consistent way to describe what each note is doing relative to the tonic.

Intervals have two parts:

• the number (2nd, 3rd, 4th, etc.)
• the quality (major, minor, perfect, diminished, augmented)

We use the major scale as a reference because it gives us a simple baseline for where 1 to 7 normally sit.

Once you know the major scale layout, any other scale can be described by comparing it to that baseline:

• if a note matches the major scale, it keeps its number
• if it is lower, it becomes flat (♭)
• if it is higher, it becomes sharp (#)

3Interval qualities

For beginners, it helps to know the two “families”:

• 1, 4, and 5 are usually in the perfect family (perfect, diminished, augmented)
• 2, 3, 6, and 7 are usually major or minor (and can also be diminished or augmented in some cases)

Examples using C as the tonic:

4Understanding the overlays

Now that intervals make more sense, the legend on the fretboard tool becomes much more useful.

Two of the filters highlight:

• 3 or ♭3
• ♭5, 5, or #5

These matter because they form the backbone of triads, the most basic chord type.

A triad is built by stacking thirds from the tonic. This is called tertian harmony.

The three chord tones are:

From those tones we get four core triad types:

Just by looking at the 3rd and 5th, you can tell what type of triad you are dealing with.

That is why the tool highlights these intervals. When you are looking at a scale pattern, being able to instantly see where the 3, ♭3, 5, ♭5, and #5 sit shows you:

• whether the sound is major, minor, diminished, or augmented
• where the most important chord tones are inside the scale
• how the scale connects to the harmony underneath it

If you want to learn more about chord theory and how other chords are built, click here.

5Characteristic tone

The major scale is the main reference point for a lot of Western music. It gives us a simple baseline for where the intervals 1 to 7 normally sit from the tonic. Once you know that layout, it becomes much easier to describe other scales by how they differ from major (or from natural minor).

We can compare many scales to these two references. Modes are the best example. Modes are usually the same as major or minor with one interval changed. That changed note is often the clearest “flavour note” of the mode. I call it the characteristic tone.
To learn more about modes, click here.

Major modes (compare to major)

Minor modes (compare to natural minor)

6Characteristic tones in more advanced modes

Up to now, we have treated modes as variations of the major scale (or natural minor). That works well because those modes usually differ by one obvious note, so it is easy to say this single degree is the flavour.

The same idea applies to other scales too. Any scale can be treated as a parent scale, and you can build modes from it. The most common examples you will see are the modes of harmonic minor and melodic minor.

Once you move into these, things get a bit more complex. Compared to plain major or natural minor, an advanced mode often changes more than one degree. That means there is not always one single characteristic tone when you compare it to major or minor.

Because of that, it is usually easier to compare an advanced mode to the closest familiar mode, rather than comparing it straight to major or natural minor. You are looking for the new change relative to something you already understand.

Reference point

Example: Dorian vs Dorian #4 (Romanian minor)

Compared to Dorian, the new unique note is #4. That is the quickest identifier for Romanian minor. To keep the Dorian feel, you still lean on the natural 6 as a strong anchor.

Example from melodic minor

Melodic minor has its own set of modes. These modes often look like major or minor with a couple of changes, so the best approach is the same: compare to the closest familiar mode first, then look for what changed.

A very common example is Lydian dominant (Lydian ♭7). It looks like Lydian, but with one important change.

Overlay note

For simplicity, the characteristic tone overlay only highlights the new unique note in the comparison you are making. Some modes technically have more than one flavour note when compared to major or natural minor, but highlighting every difference at once can be overwhelming. The point of the overlay is to show you the quickest identifier, not every detail.