Guitar Scale Theory

A Gentle Introduction to Guitar Scale Theory

jazz fundamentals Mar 24, 2021

The Quick Guide to Scales and Modes for all Jazz Guitarists

The major scale is the single most important thing to know about guitar scale theory. You’ll learn this “quasi-magic” formula to build the major scale in any key.

This is a gentle introduction to guitar scale theory so if you don’t read music, (“notes” on the staff) don't worry about it because even if you’ve never encountered any music theory in the past, this is a great place to start. So, take your time and don’t be afraid to ask questions!

Over the course of this guitar scale theory article about scale construction, you’ll discover music theory info about the major scale, how to read key signatures, modes and more.

So, ready for your first leap into guitar scale theory? Let's go!


Before we start...

What is a Scale?

A scale is an arrangement of tones ordered in a pattern ascending or descending.

Take note that:

  • Scales in this article have 7 notes.
  • The distance between every two consecutive notes is the interval of a second. We have major second (2 frets, also called whole-step) and minor second (1 fret, called half-step).
  • We’ll start in the key of C (C D E F G A B C) and we’ll go step by step through *other* keys.
  • We will be using sharps (#) to raise notes one half step and flats (b) to lower notes one half step in all following guitar scale theory parts of this article.
  • We refer to "guitar scale theory" because this site is for guitarists but a lot of the theory in this article is applicable to music in general.

Table of Contents

Part 1........................................................ The Formula
Part 2........................................................ Building All the Keys (Signatures)
Part 3........................................................ Intro to Modes
Part 4........................................................ 21 Most Common Modes

Part 1

Guitar Scale Theory and the Major Scale Formula

First of all, to “build other keys” with guitar scale theory, we need to make sure that we understand the foundation really well.

Therefore, the formula for major scale construction is as follows.

W – W – H – W – W – W – H

(W stands for whole-step and H for half-step)


We’ll use the C major scale to exemplify the distance between every two consecutive notes within the scale.


__whole step__


__whole step__



__whole step__


__whole step__


__whole step__



Especially relevant to notice is that the half-steps are between the third & fourth degrees plus the seventh & first degrees of the scale (E-F and B-C in the case of C major). The placement of these half-steps in two specific locations creates this scales' unique sound characteristics.


Looking at a piano keyboard can help to visualize the concept.

In summary, there’s no black key between E-F and B-C, resulting in the half-steps.


Building Scales in Other Keys

Here’s the fundamental trick in guitar scale theory. -----The structure is constant!-----

It probably seems like this isn't a big deal at this point, but this simple idea allows you to build scales in 12 different keys (or more).

Simply use the original WWHWWWH formula and start on a note other than C. As a result, the scales basically build themselves!

The layout of the notes doesn’t even change (see keyboard), but we’ll have to adjust with some sharps and flats as we start the formula on other notes than C.

Seems like a good time to work through an example. Let’s spell this major scale in the key of G major, and while doing so, be sure to verify that we’re respecting the formula (WWHWWWH).

Go slowly here and refer to the above keyboard for a visual reference.

G A (check) — Whole Step
A B (check) — W
B C (check) — Half Step
C D (check) — W
D E (check) — W
E F (oops!) — ???

It seems like we need a whole-step at the E-F point, but we know (from the keyboard layout) that between the E and F notes lies a half-step so, let’s raise the F note a half-step up so it becomes F#. Therefore, we make it conform to our formula.

Let's continue our verification process.

G A (check) — Whole Step
A B (check) — W
B C (check) — Half Step
C D (check) — W
D E (check) — W
E F# (check) — W
F# G (check) — H

Perfect! As a result of starting on the G note, (G major scale) we get the following notes according to the formula; G A B C D E F# G.

So, in order to respect the scale theory formula, we now understand that the key of G major requires an F-SHARP note for it to work smoothly. So in fact, “the structure is constant”. This is an especially relevant concept to remember because you will never get lost creating a scale.


More Keys

In addition to the G major scale example above, let's try the major scale in the key of F major this time.

F G (check) — Whole Step
G A (check) — W
A Bb (check) — Half Step
Bb C (check) — W
C D (check) — W
D E (check) — W
E F (check) — H

Perfect! The F major scale = F G A Bb C D E F. Did you subsequently notice we had to utilize a FLAT this time to stay true to the formula?

We could carry on with this guitar scale theory business, but I’d rather give you a generalized process at this point so you can apply it on your own right away.


The 4-Step Process to Building a Major Scale in any Key

  1. Decide on the key and write down the letter-name of the first note.
  2. Write down all consecutive letter-names of all the notes until you reach your starting point again (total 8 letters on the page). In step 2, DO NOT write any flats or sharps (just the letters).
  3. Verify that the scale complies to WWHWWWH from the very first note.
  4. Whenever two consecutive notes do not agree to the formula, simply adjust with sharps OR flats (but never both).

This is extremely important! Do not mix flats and sharps in the same major key!!!

At this point you should take a sheet of paper and write out the keys of D, A, Bb and Eb. Simply write “WWHWWWH” at the top of the paper to remind you of the scale theory formula because using it like this will help increase and consolidate your own understanding of this foundational formula.

So, did you notice what happened? During the process, we were adding more and more alterations (flats or sharps) as we got further and further away from the “natural” notes (white keys on the keyboard) of the C major scale.


Guitar Scale Theory and Uniqueness

A noteworthy fact is every scale has its own amount of sharps or flats. That’s right! As a result, it’s the easiest way to identify a tonality or key of a piece.

So, the “key you are in” can be uniquely determined by what notes are altered with sharps or flats, because if I tell you “one sharp”, you can immediately take for granted that we’re in G major. If I say “one flat”, it’s F major. See both examples above.

We’ll continue along these lines and discuss how to know in a glimpse what key we're playing in.


Part 2
Guitar Scale Theory and Key Signatures

Guitar Scale Theory and Key Signature Introduction

Key Signatures are like the “scale theory shortcut” invented a long time ago, probably by European classical musicians.

Every major key is unique. As a result, any given major scale carries its own signature which shows the amount of flats or sharps.

Each key signature is unique and never duplicated.

So, the “key you are in” can be uniquely determined by what notes are altered with a sharp or flat.

For example, if I tell you the key signature has “one sharp”, you can immediately deduce that we’re in G major. If I say “one flat”, it’s F major.

Here's how it looks on the staff.

Key Signature is G major (one sharp). Key Signature is F major (one flat)

Jazz musicians say “what’s at the clef” to quickly glean what key a piece is to be played in, and in a single glimpse at the beginning of the score, knowledgeable musicians know immediately in what key they’re about to play in.

Also, the sharps or flats in the key signature are “carried” throughout the piece unless they’re cancelled by a natural sign.

So, the sharp indicated in the key signature means all F's are sharp unless otherwise indicated. Notice above in G major, there is an“F natural” marked near the end. As a result we don't have to read or write a sharp beside every F in the above notation because notation often looks "busy" enough as it is.

In summary, you simply have to write it once at the beginning and you’re done! Thank European classical composers for that.

Guitar Scale Theory and ALL key Signatures

So, how many key signatures can there be? Well, as many as it takes to find all major keys! (If you think about it, you can only have a maximum of 7 sharps or 7 flats for any given key. Any major scale has seven notes, and each note can only be altered once. Consequently, that’s a total of 14 possibilities and if we count the key of C major (no flats and no sharps), we have a total of 15 different key signatures for major keys.

Of course, we have some repetitions, called enharmonic tonalities (same sound but appears different on paper such as Cb=B, C#=Db, F#=Gb). Not counting those, we would of course only have our 12 keys from the western civilization musical system.

So, how can we find ALL the keys and memorize what key has 3 flats and what key has 5 sharps, and so on?

Well, I believe the best solution is;

  1. to truly understand where the key signatures are coming from (you should be pretty close by now!);
  2. know *in what order* the alterations appear on the staff, and
  3. finally to build, memorize and practice common keys up to 4 or 5 alterations and the rest will take care of itself.


Guitar Scale Theory and Key Signature Order

The key signatures for all the major scales obey the rule of “gravity” regarding notes. Hence, you can start in any major tonality and if you move towards a new key, the INTERVAL in which you jump will determine the signature of the following key.

As a rule of thumb for guitar scale theory, key signatures are added or subtracted one by one in cycles of fourths and fifths. All the previous flats/sharps remain, but we add ONE as we go along each interval. It’s much easier to stick to that “move” and add or remove the alterations one by one. So, moving;

  • UP a fourth adds a flat or removes a sharp, and
  • DOWN a fifth does the same thing.
  • DOWN a fourth removes a flat or adds a sharp, and
  • UP a fifth does the same thing.

Please note:

Going down a fourth is the same as going up a fifth. For instance, C to G is five degrees C being 1 and D being 2 and so on.
Going down a fifth is the same thing as going up a fourth. For instance, C to F going down in tone is a fifth (count them on the above keyboard).


Up a fourth (or down a fifth) ADDS a flat.


Up a fifth (or down a fourth) ADDS a sharp.


Also, it is critical to know that flats actually appear in the order of the ascending cycle of fourths where the first flat is “Bb”, the second is “Eb”, the third is “Ab”, and continuing in this manner. The same applies to sharps, but in the descending cycle of fourths order.

That's systematic scale theory!

So, from that point, it becomes pretty obvious how to build all the 15 available major key signatures. Simply start with G major (one sharp) or F major (one flat) and go “all the way through”. You can always go back to the formula WWHWWWH but it will take you forever! (-:

Sharps and Flats in “Table Format”

Order of Flat keys
0: C major
1: F major
2: Bb major
3: Eb major
4: Ab major
5: Db major
6: Gb major
7: Cb major
This was “up a fourth”


Order of Sharp keys
0: C major
1: G major
2: D major
3: A major
4: E major
5: B major
6: F# major
7: C# major
This was “up a fifth”

Once you understand this well, it becomes easy to build “the full circle” and see all the 15 major signatures in one table (or picture) of scale theory. I’ve used ascending fourth cycle, but you could also use ascending fifths.

Order of Key Signatures (both flats and sharps)
0: C major
1 flat: F major
2 flats: Bb major
3 flats: Eb major
4 flats: Ab major
5 flats: Db major … OR … 7 sharps: C# major
6 flats: Gb major … OR … 6 sharps: F# major
7 flats: Cb major … OR … 5 sharps: B major
4 sharps: E major
3 sharps: A major
2 sharps: D major
1 sharp: G major
0: C major
This was “up a fourth”

The Cycle of Fourths (or Fifths) Chart

Move through the keys by
circling in both directions.

Key Signatures in Minor

This is probably pretty easy for you because you already know your major scale key signatures from earlier in this article and you can simply rely on the relative minor-major principle described here.

  • In a major key, the relative minor lives on degree VI. For instance, C major scale has the relative minor of A minor scale.
  • In a minor key, the relative major lives on degree bIII. For instance, C minor scale has the relative major of Eb major scale.

Both relatives have the same key signatures.
C major and A minor have no alterations.
Eb major and C minor have three flats and so on.

So, simply keep in mind that whenever we see key signatures, they might imply a minor scale OR a major scale. The tunes in a minor tonality may have more accidentals written throughout the piece if they utilize part of melodic minor or harmonic minor. As a result, some degrees must be raised for the scale theory to work.

Take as an example a C minor (natural) which has three flats, C D Eb F G Ab Bb C, however, the same notes are in Eb major because they’re relative as discussed in the above relative minor-major principle.

If the whole tune, or part of the tune has those scales, then the A and B notes are natural in the C melodic minor scale, (C D Eb F G A B C) and only the B note is natural in the C harmonic minor scale (C D Eb F G Ab B C).

Consequently, some “accidentals” (sharp or flat alterations) in a piece will be required in order to supplement the information found in the key signature.


Guitar Scale Theory and One last *Trick*

One of the most relevant pieces of advice about memorizing key signatures is to learn up to four sharps and four flats and then use a little shortcut for more complicated keys.

  1. First of all, memorize flat keys in this order: C, F, Bb, Eb, Ab
    and sharp keys in this order: C, G, D, A, E.
    This is from zero to four alterations.
  2. THEN, when a key signature has 5, 6 or even 7 alterations, you can then subsequently think of the “opposed” key that contains the same amount of natural notes.

This one could probably use an example to demonstrate, so let's say there are 6 sharps at the clef, which results in only one natural note to fulfill the required seven notes of our scale. Use that one natural note and simply think of the key that has ONE flat, because that’s it’s "sibling". So, you deduce the little brother is F major because it has one flat, and then you mentally apply the sharp to it (because remember we are dealing with 6 sharps in our key signature for this example) to deduce the key that contains 6 sharps, which is F# major.

In summary of this example, we used the one natural F from the original key signature, threw the sharp on it because we are dealing with sharps and that F became our F# major key signature, and that's the key that our piece is played in! Now that's a shortcut! (Even though it was verbose getting here.)

Another "One" for You

The same thing can be seen in this example, but this time you see 5 flats at the clef so we can deduce there’s two natural notes this time instead of one, because there is already 5 flats (must have 7 notes total). Most of all, think of the key that contains 2 sharps to help get us there (D major has 2 sharps). So, mentally add a flat to D Major (because we are dealing with flats in our key signature) and voila, you can therefore deduce that the key signature with five flats is Db major.

Furthermore, if we compare the keys of F# and F, we notice that all the sharp notes in F# become natural notes in F … and all the natural notes in F# become flat notes in F. (Rethink the same process for yourself with a flat key, say Gb major.)

As a result of this information, (and some pondering) guitar scale theory just got easy!

So What Else?

That’s it, you’re done! If you know this, you’re set for life, because everything else in scale theory (modes, symmetrical scales, improvisation, harmony, etc.) actually comes from this idea of the WWHWWWH formula and the key signatures.

This knowledge of key signatures is important, but please keep in mind, the more chromatic the music becomes (out-of-the-key) the less the signature is useful. Some “modern” (from recent years) jazz is written without key signatures because of its complexity. In this case, all alterations are accidentals, note-by-note. No scale theory needed. (-:

We’ll now discuss a subject that seems to confuse everybody … modes!


Guitar Scale Theory:
Part 3
What Are Modes

Guitar Scale Theory Modes Introduction

If you’re reading this article, you’ve probably heard about modes somehow, somewhere. It still fascinates me that there’s this big aura of mystery around what a mode actually is!

A mode is a scale built from NOT starting on the root of an already existing familiar scale (the “parent scale”).

If C major scale is our parent scale, just start on a different note such as D and you are then looking at the second mode of C major, also called D dorian.

The implications of starting a scale from a different root are huge and it’s not just about playing the exact same tones in a different order, because seeing everything from this “modal” perspective changes the overall “gravity” of the notes. It changes harmony and everything else. D dorian doesn’t imply a beautiful C major CHORD anymore, because it now sounds like Dm7!

The major scale theory formula and the order of the intervals (WWHWWWH) is still there, but it’s going to be re-arranged in the case of D dorian, to WHWWWHW (moving everything up one notch).

Think of the C major scale as a solar system because the notes organize themselves around the “gravity” of C. When we play in D dorian, the orbits are completely re-organized and everything revolves around D. But, all the same “planets” and “moons” are there! Same notes, same order (formula), same everything but with different implications.

So, in summary, a mode is still a scale. We just call it a mode because we know it relates back to a well know parent scale. Therefore, we can build a mode upon each note of the major scale, and that's exactly what we’ll do now.


Guitar Scale Theory and Modes from the Major Scale

We’ll use the key of C major to demonstrate and all the starting notes will be shown, subsequently demonstrating the 7 modes of major.

I’ll also include the formula using scale degrees to explain the modes because the formulas will show you how much different each mode really is from anything else! It’s the aural perspective on each mode that makes it sound the way it sounds, and not just the notes contained within it.

As a result, the modes of C major are seven distinct ways of looking at the exact same thing.

The modes are:

1: C Ionian (aka major scale)
Formula: 1 2 3 4 5 6 7
C major chord and the foundation of it all.

2: D Dorian (aka Dorian minor)
Formula: 1 2 b3 4 5 6 b7
Implies a Dm7 chord and often used in jazz. It’s the iim7 chord.

3: E Phrygian
Formula: 1 b2 b3 4 5 b6 b7
This is like an Em7 chord with a b9 and often used over E7sus4(b9).

4: F Lydian
Formula: 1 2 3 #4 5 6 7
Same as a major scale with a #4. (Think of F major with a “B natural”.)

5: G Mixolydian (aka dominant)
Formula: 1 2 3 4 5 6 b7
Same as a major scale with b7. Implies a G7 and has bluesy type feel. It’s the V7 chord.
The is the dominant sound.

6: A Aeolian (aka Natural Minor)
Formula: 1 2 b3 4 5 b6 b7
The simplest and “most stable” type of minor tonality. Sounds like Am7.

7: B Locrian
Formula: 1 b2 b3 4 b5 b6 b7
A Bm7(5) sounding mode and a very “odd” mode.

In addition, to further understand these modes and all the scale theory, please also see “up to the 13th” on the “Chord Construction – Part 4” article.


Guitar Scale Theory and “Seeing” C Major Modes

style="text-align: center;">7 modes of C Major Scale

Guitar Scale Theory and Key Signatures for Modes

You can often use the signature of the parent major scale.

Let’s say you were playing a tune in C major (key signature is explicitly C major), but the key signature can still remain the same!

“What! I need to learn ALL the modes!!!”

Just relax and we'll get there a lot easier than you think, because here’s a simple way to hear and learn the modes.

Remember that you are not “learning all the modes”, you are simply looking at the major scale from a different perspective each time, so it’s nothing new and therefore no need to worry about a massive work-load here.

Practice steps:

  1. On the guitar, find all the notes of the C major scale on the 2nd (B) string. The frets are 1 3 5 6 8 10 12 13, so play the scale a few times and memorize the sounds and location of all the notes.
  2. Strum a simple C major chord and possibly let a “C” bass note ring out by tuning down your lowest string, and then,
  3. explore the C major scale on the 2nd string by relating the sound to that “C” bass note.
    As a result, you are now playing in C Ionian.
    Stay on that “sound” for about 3-5 minutes. and listen and explore.
  4. Repeat steps 2, 3 and 4, SEVEN times by changing the bass note to D, E, F, G, A, and B, and you will have “learned” the modes of C.

So, whenever you think you have to learn 532 new fingering patterns on the fretboard and you’re stressing out about “all the modes” in scale theory, just come back to this exercise and get back on track.

Most of all, don't learn all the modes, but do learn to see common scales from this new perspective, and that's the trick.


Guitar Scale Theory: Are there Modes in other Keys?


If C major has D dorian, then G major probably has A dorian, and F major has G dorian and so on, because each individual major key has its own seven assorted modes, and most importantly, they’re always in the same order with the same implications. However, they’re just in a different key!

Remember the idea of “constant structure”? Well, this is what I mean.

Finally, in Part 4 we’re going to take a look at modes through two more “parent scales”, such as C melodic minor and C harmonic minor.

Part 4

Guitar Scale Theory

Guitar Scale Theory and 21 Modes

We can build 7 modes upon a parent scale of 7 notes as discussed above, so in this part I’ll simply list 21 modes, as a result of being the 7 modes of C major (C D E F G A B), the 7 modes of C melodic minor (C D Eb F G A B), and the 7 modes of C harmonic minor (C D Eb F G Ab B).

But first, some general advice.

Most modes of major and melodic minor are in common use today and as a result I’ve already created some other articles about the “dominant” sounds in these modes. Consequently, it's a good read and the links are within this part of the article too, so read on.


Modes from the Major Scale

We've already talked about these in Part 3 so, if you want to review them here's a href="#h144skppthcfvql84cm25m6bj1w7j68r">link.

Guitar Scale Theory and Modes from the Melodic Minor Scale

Please remember that the C melodic minor scale is built like this:
C D Eb F G A B (or 1 2 b3 4 5 6 7.


1: C Melodic Minor
Formula: 1 2 b3 4 5 6 7
Our “parent scale” here.

2: D Dorian b2
Formula: 1 b2 b3 4 5 6 b7
Implies a Dm7(b9) chord and kind of odd.

3: Eb Lydian Augmented
Formula: 1 2 3 #4 #5 6 7
A “hyper”, major-sounding scale, so think Eb major with an A and B natural.

4: F Lydian Dominant
Formula: 1 2 3 #4 5 6 b7
Same as Mixolydian but with a #4. It’s F7(#11) but could think F7 with “B natural”.
The is the Dom7(#11) sound.

5: G Mixolydian b6
Formula: 1 2 3 4 5 b6 b7
Same as Mixolydian but with b6. It’s G7(b13), however, could think G7 with an “Eb”.
The is the Dom7(b13) sound.

6: A Locrian “Natural 2”
Formula: 1 2 b3 4 b5 b6 b7
The most straight-forward m7(b5) and contains a half-diminished-type sound.

7: B Super Locrian (aka altered scale)
Formula: 1 b2 b3 b4 b5 b6 b7
Very “odd” and “tense” mode, but very useful on altered dominants.
This is the Dom7(alt) sound.

Furthermore, please see “up to the 13th” on the “Chord Construction – Part 4” article for more information.


Guitar Scale Theory and Modes from the Harmonic Minor Scale

Please remember that the C harmonic minor scale is built like this:
C D Eb F G Ab B (or 1 2 b3 4 5 b6 7).


Mode 1: C Harmonic Minor
Formula: 1 2 b3 4 5 b6 7
Our “parent scale” here.

Mode 2: D Locrian “Natural 6″
Formula: 1 b2 b3 4 b5 6 b7
Not used much.

Mode 3: Eb Ionian Augmented
Formula: 1 2 3 4 #5 6 7
Think major scale with a raised fifth, but also not used much.

Mode 4: F Dorian #4
Formula: 1 2 b3 #4 5 6 b7
Uncommon but usable and creates a Fm7(#11) sound.

Mode 5: G Mixolydian “b9 b6” (aka Phrygian Major)
Formula: 1 b2 3 4 5 b6 b7
Called “harmonic minor of destination” and used a lot on altered dominants.
This is the Dom7(b13, b9) sound.

Mode 6: Ab Lydian #9
Formula: 1 #2 3 #4 5 6 7
A crazy and uncommon type of major mode!

Mode 7: B Altered Dominant bb7
Formula: 1 b2 b3 4 b5 b6 bb7
Too odd to be true! Ouch.

In addition to understanding these modes, please see “up to the 13th” on the “Chord Construction – Part 4” .


Guitar Scale Theory Modes Conclusion

And that’s a wrap, so please keep in mind that even if all the modes look cool “on the page”, it’s always a matter of how you can use, hear and apply them with taste, so go back often to the href="#h426skpptuoegf595fymxmyvn1xc35mj"practice method for the modes I’ve outlined in Part 3.

Most of all, don’t allow yourself to get overly excited about theory and don't forget to take a step back once and a while and examine everything with your ears. It’s not because you understand something intellectually that you’re automatically granted the wisdom to make beautiful music right away, so practice, listen and explore!

Most of all, enjoy!


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