The Only Theory Lesson You’ll Ever Need – Part 2


In Part 1 of The Only Theory Lesson You’ll Ever Need, we covered the foundational elements of music theory: the musical alphabet, the concepts of whole steps and half steps, and the use of accidentals (sharps and flats) to fill in the blanks between natural notes.

In Part 2, we’ll use that information to take the next step forward: constructing major scales and understanding keys.

Major scale construction is one of the most important things you could ever learn in music theory, since everything else is built upon this foundational concept. And gaining insight into scales and keys teaches us how notes are related within a musical “family”, and what notes tend to complement each other in melodies, riffs and solos. Let’s get it on!

Building the Big Kahuna

The major scale is the single most important element of music theory. It’s the granddaddy of all musical concepts, the Big Kahuna. Call it what you will – all other musical concepts flow from the major scale, so it’s critical that we learn to construct it correctly.

A major scale is a sequence of seven notes (plus the octave note) that sounds like the familiar do-re-mi-fa-so-la-ti-do. It can be built from any starting pitch, and that pitch gives the scale its name. For example, if we build the scale from the starting pitch C, we would get a C major scale. Makes sense, huh?

Constructing the scale correctly is simply a matter of picking a starting note (which is called the “Root”) and then applying the major scale formula of whole steps and half steps, as shown here:

ROOT – WHOLE – WHOLE – half – WHOLE – WHOLE – WHOLE – half

You might also remember it as, “two wholes and a half, three wholes and a half”.

It’s because all major scales follow the same formula of whole steps and half steps that we can achieve the same do-re-mi sound off of any starting pitch. As long as we follow the formula accurately, we’re able to maintain consistent relationships between the notes, which ensures that all of our major scales – no matter the starting pitch – sound like do-re-mi.

Following the Formula

Let’s build a major scale from scratch. Using our previous example of C as our starting pitch, we’ll apply the major scale formula as follows:

Starting pitch (“root”) = C
C + whole step = D
D + whole step = E
E + half step = F
F + whole step = G
G + whole step = A
A + whole step = B
B + half step = C

The C major scale, then, consists of the notes C-D-E-F-G-A-B-C, and, when played, it sounds like do-re-mi. You may also note that the C scale is constructed from natural notes only, as it needs no accidentals (sharps or flats) to fulfill the formula. Since all major scales are unique, the C scale is the only one with no accidentals; every other scale has its own number of sharps or flats.

Once you’ve learned how to construct a scale, it’s good practice to also think of the notes in terms of their number, or scale degree. For instance, in the C major scale, C is the “1”³ (or root note), D is the “2”³, E is the “3”³, etc. This will come in handy later, when learning to build chords and transpose to other keys.

Using Sharps

Before we move on, there are two special rules to follow regarding major scale construction:

1 – All letters must be represented once and only once.
2 – We use either sharps or flats to complete the formula, never both.

Keeping this in mind, let’s try another scale from a different root, or starting pitch: G.

Starting pitch (“root”) = G
G + whole step = A
A + whole step = B
B + half step = C
C + whole step = D
D + whole step = E
E + whole step = F#
F# + half step = G

The G major scale, then, consists of the notes G-A-B-C-D-E-F#-G.

Why F#? Remember that E/F are natural half steps. However, in order to fulfill the formula, we need a whole step above E, so we would travel a half step to F and another half step to F#.

Picking the note F# rather than Gb, its enharmonic equivalent, is important because it follows the “each letter is represented once” rule. It also creates the concluding half step to G – perfect!

Using Flats

For a final example, let’s construct the major scale starting from F so we can see accidentals from a different perspective.

Starting pitch (“root”) = F
F + whole step = G
G + whole step = A
A + half step = Bb
Bb + whole step = C
C + whole step = D
D + whole step = E
E + half step = F

The F major scale, then, consists of the notes F-G-A-Bb-C-D-E-F.

Why Bb? Remember that A and B are a whole step apart. In order to fulfill the formula, though, we need a half step above A. Since we’ve already used the note A, we would not call the target note A#, but rather by its enharmonic equivalent, Bb. The pitch Bb is a whole step from C, so it fulfills the formula moving forward as well.

I would recommend that you practice writing out some of the more common scales. Having major scale construction at your fingertips is a great foundation for learning about chord construction, one of the major elements of guitar theory. The scales I usually recommend – besides C, G and F – are: D, A, E and Bb. As a challenge, try writing them out now following the above process and I’ll put the answers at the end of this lesson post. Feel free to download and use the handy-dandy Major Scale Worksheet I’ve put together.

Major Scale Worksheet (PDF)

The Key

Of course, the major scale is what a musician is referring to when he/she says, “This song is in the key of ____.”

The key is simply the family of notes – the major scale – that makes up the sound of your song. The central note, or key center, of your song will be the root note of your major scale. So if the song is in the key of G, then the root note G will be the main note of your song, and all other notes relate to it.

The Key of G

Music Reading Alert!: The key can also be determined by looking at the far left of the staff on traditional music notation. The accidentals in the key of the song will be represented on their respective lines of the staff in what is called the key signature. So a song in the key of G, for example, would have one sharp (F#) located on the top line of the staff, which is where the F note is positioned. This indicates to the musician that all F notes are to be sharp throughout the song, keeping us nicely in the key of G.

The notes that occur naturally in any key – that is, the notes that we derive by using the major scale formula – are called diatonic notes. They are “of the key”. Most of the notes of a typical pop song will be diatonic. However, if all songs contained only diatonic notes, then all songs would sort of sound the same. To add a little spice to your musical gumbo, many songwriters will sprinkle in a few notes that do not occur naturally in the key. These “outside” notes are called non-diatonic.

Now before any theory nerds beat me to the punch, songs do not only have to be in major keys, with major scales as their basis. Some songs are in minor keys, or even use modes (variations on the major scale, which we’ll save for a future lesson). But minor keys and modes flow from the major scale concept, so for this lesson, let’s just stick with the major scales/keys to avoid unnecessary confusion.

In Part 3 of this series, we’ll explore the final piece of the theory puzzle: harmonizing the major scale with chords and learning to transpose to other keys. Stay tuned!

Answer Key

D Major Scale = D-E-F#-G-A-B-C#-D
A Major Scale = A-B-C#-D-E-F#-G#-A
E Major Scale = E-F#-G#-A-B-C#-D#-E
Bb Major Scale = Bb-C-D-Eb-F-G-A-Bb

How’d you do?

More from this series

About Jim Bowley

Jim Bowley spent 20+ years as a performing and recording guitarist, vocalist and songwriter. He currently spreads the guitar gospel via his website,, and his Bel Air, Maryland-based private studio. You can also find Jim on Facebook discussing all things six-string.

Comments [8]

  1. Gary Clements says:

    This lesson is confusing, as I find most when studying music, in that rule number 1 states: All letters must be represented once and only once.
    However, reviewing each major scales’ components I find the root note repeated twice in all cases – which seems to be counter to rule number 1.
    Please explain.


  2. Gary,

    Sorry you found it confusing! Let me try and clarify.

    Remember that the musical alphabet is a LOOP of 7 letters, with no true beginning or end. Therefore once you pass through 7 notes, you “begin again” at note 8.

    In a major scale, the 8th letter is exactly the same as the first – an OCTAVE higher. When I set up the rule of “every letter once and only once”, I was referring to our inclusion of accidentals and how that sometimes presents a dilemma when writing a scale (the example being, do I use F# or Gb? Since we already have a G, we can’t also use another type of G, such as Gb.)

    Please be sure to check out PART 1 (linked at the start of the lesson) and specifically the section “The Musical Alphabet” – I think that will help greatly!


  3. John Gelbart says:

    Hello Gary,
    I think JB’s explanation is spot-on and very very clear. If you check out his answers to the scales you’ll notice that all letters in the scale are represented only once, within the octave. I’m sure after a bit of practice you’ll grasp the idea and the principle will be clearer.

  4. Dave Combs says:

    Hey Jim:

    First time writer, and I’ve just found your site and I’m LOVING what I see on it. I’d love to see more of your bass lessons, because that’s where my aspirations lie.

    A quick question concerning determining what key a piece is in… I played clarinet in middle and high school (I’m forty-something now) so I can read music and hold my own on that instrument; you can’talk dirty” to me for your answer. Basically, in the example above you say that the key signature with one sharp (F#) translates to the key of G (G major). How can you deduce what key something is in based on the number of sharps or flats in the signature? Is it just rote memorization (one sharp on F = G major, two sharps on… = …), or is it because, as an example for the key of G, that there is only ONE possible major key that has only one sharp?

    That’s the part that I never really got about music theory, and I never took a theory class. (It wasn’t offered, but in all honesty I’m not sure I would have taken it anyway!) The kids who understood this part of it could, by memory I thought, just puke out the name of the key as soon as they saw it. I never thought it to be too useful, other than I had to remember to play the sharps and flats as written.

    Can you clear that up for me? I’d appreciate it very much. And again, I LOVE this site and I’ll be referring to it a lot as I’m beginning to tackle the bass.

    • Hi Dave

      If you’ll allow me to jump in for Jim, you can find a handy key signature chart in the following lesson:

      An easy way to remember these signatures without a chart, at least as far as major keys are concerned, is as follows:

      For sharps, the last sharp at the right end of the key signature is always a half-step lower than the root note of the key. When F# is the only sharp, the note a half-step above it is G. When you’ve got two sharps, they are F# and C#, with the C# being the farthest to the right. A half-step up from C# is D, which is the major key with two sharps.

      For flats, you have to remember that one flat is the key of F. After that, the note of the next-to-last flat in the key signature is the root note of the key. So when there are two flats, they are Bb and Eb and the key is Bb major. When there are three flats, they will be Bb, Eb and Ab and therefore the key will be Eb major.

      It’s important to know, though, that this only applies to major keys. Every major key has a relative minor, whose root note is the sixth note of the major scale of the original key. So when you see a key signature with no flats and no sharps, it is possible that it might be Am instead of C.

      Hope this helps. Welcome to Guitar Noise, by the way. Please feel free to post any other questions you may have either here or on our Forum page.


  5. Dave Combs says:


    If I could email you a pizza, I would – your explanation flipped the switch on a brain cell I forgot long ago. I thought I heard somewhere that it involved, like you said, the last incidental on the staff.

    Thanks again. I’m going to print this out and keep it in my bass bag (well, once I get it out of layaway, that is).

    • Hi Dave

      A thank you is just as good as a pizza. However if you should ever be out in Western Massachusetts, let me know and maybe we can work out lunch somehow!

      Serious, glad to be of help. Please feel free to post again or email me directly if you have other questions. Also be sure to make use of the Forum pages at Guitar Noise. There are a great many folks here who are more than happy to help out however they can when it comes to making guitar (and music) easier.


  6. Hi Dave – glad you liked the lesson! And thanks to David for jumping in and providing a great and clear explanation to the key signature question.