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Music Theory

By Milo McNally

In these lessons I will try to explain the fundamentals of music theory as simply as I can.

While each part may seem short, take your time and see how you can apply each one to your musical journey.

Each section will build from the last, so if you are lost then it may be that you needed more time on a previous section.

With all that out of the way. Let’s start our first lesson.

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Music

To understand music theory we first have to understand that:

✨ Music is just nice sounds. ✨

Everything in music essentially comes back to the fact that music sounds good. No matter how complicated it may seem, music is about creativity and feeling. If it sounds good, you’re doing something right.

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Sound & Pitch

Sound is made of waves through the air.

The speed of the wave makes the sound higher or lower. We measure this by the amount of waves per second or “frequency.” This unit of measurement is called “Hertz” (hz).

We call this “Pitch” and for music we have named 12 of these pitches. Despite there being a wide range of frequency we can hear, there is no need to name any more pitches. To explain this further we’ll look at “A”.

The pitch we hear at 440hz has been called “A.”

If you divide that by 2 to 220hz our brains also hear “A.”

So too if you keep halving. So 110hz = “A”, 55hz = “A” and so on.

This also works when doubling. 880hz = “A”, 1760hz = “A” and so on.

So there is no reason to name any more pitches because to our ears they loop back around to the beginning.

The distance between each of these loops is called an “Octave” which we have divided into 12 and named these divisions “Notes”. The naming system of the notes will be explained over the next few lessons.

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Notes

The pitches we learned about previously are more commonly known as “notes.” There are 12 notes in total. 7 natural notes and 5 accidentals (The ones with the # and ♭). This is where the first bit of memorisation comes in.

Each of these notes are the same distance from each other. I will be referring to this distance as a “half step.”

You’ll notice that some of the notes have 2 names; these are commonly referred to as the “sharps” (#) or “flats” (♭). It should be noted that there is nothing special or different about these notes. Sharp means up a half step, and flat means down a half step.

Also

It’s simply a naming system to help us not have the same letter notes in our scales.

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Scales

It’s not the notes themselves that sound musical, but rather the distance between them. All 12 notes played in sequence (The chromatic scale) doesn’t really make you feel much. So we made more scales with different spacings that have different feelings. We will focus on just 1 for now:

The Major scale

Now we are starting to skip notes. I will be referring to this as a “whole step”.

As said before, scales are not the notes, they are the steps between them.

So (more memorisation here) the major scale steps are: Whole, whole, half, whole, whole, whole, and a half step brings us back to the start.

You can start this combination of steps on any note and, while it will sound higher or lower, everything else will sound the same.

Once you're happy with that it's time to be able to name the notes properly. The naming system will be fully explained in the next section.

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Keys

When you play a scale the key is named after the starting note (also called the root note) and the scale. For example a major scale played starting on A is called A major.

The names of the notes in the key should then follow the A through G format. Whatever key you're playing in should never have 2 of the same letter. This is what decides the name to give our accidentals.

There’s an important pattern emerging here. Your key will only have sharps or flats, not both. Also, each key has a different number of sharps and flats.

When starting your key on an accidental you can choose to call it one or the other, however one is usually less complicated than the other.

While they are both correct, G# doesn't need to be doing all that. Lets just call that one A♭ and forget about it.

We can then use the number of accidentals to help learn the different keys to play in. This is the reason most music theory lessons start with the key of C major, as it contains no accidentals. I will also be using it in future lessons.

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The Numeric System

Now that we have learned that all our major scales roughly sound the same, we need a system to talk about the notes that can apply to all keys and by assigning a number instead of a note in between our whole steps and half steps, we can do just that.

Notice that there are two 1’s. Just like how our notes loop, so do the numbers.

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The Minor Scale

It’s time to learn our next scale. The minor scale. Like any other scale it's got its own set of whole and half steps. This time (memorisation time) it's: Whole, half, whole, whole, half, whole, whole.

This works just like the major scale. You can:

- Start this set of whole and half steps to any note and it will sound the same.

- Name the sharps and flats from A to G with no double letters.

- Assign numerical values to play in different keys.

Now let’s compare the 2 scales. You may recall when I said that different scales have different feelings. It’s often stated that the major scale sounds “happy” and the minor sounds “sad.”

Also like keys, each minor key has different numbers of accidentals. Just like the key of C major, the first minor scale taught is A minor as it has no sharps or flats.

Wait a second… Why does A minor have the same notes as C major?

Let’s find out.

Relative Minors

Every major scale has its relative minor. This means that they share the same notes and chords.

It's not just C major and A minor that have this relationship. Remember that every major scale has the same order of steps and so does every minor scale.

As a result of the whole and half steps aligning, the relative minor can always be identified as the 6th note of the major scale.

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Intervals

When you hear a piece of music, unless you have perfect pitch, it is not possible to identify the key or exact notes being played by ear alone. What we can identify is the distance or “intervals” between the notes.

By this point you have already learned a bit about intervals. Whole steps and half steps are intervals, and when you number the 7 notes in your scale they are all intervals, but I have to get a bit technical here.

These are proper names of the intervals. Remember that all our notes are a half step apart so our intervals are measured in half steps.

There is no need to memorise all that right now. Whether you're working in a major scale or minor scale it's fine to just call them first, second, third, fourth, fifth, sixth, seventh and octave.

What will be important in the next lesson are the major and minor thirds, and the perfect fifth, which I will just be calling the fifth.

Also a half step and a minor second are the same thing. A whole step and a major second are the same thing. There's more than one name for everything so don't worry about it.

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Chords

Like the scales, chords are movable patterns of whole steps and half steps. However this time the notes are played simultaneously (in harmony).

Just like the scales there are different chords that evoke different feelings. We will be focusing on and comparing the 2 main types of chords. The major chord and the minor chord.

The major chord is made from the root, major third and perfect fifth.

The minor chord is made from the root, minor third and perfect fifth.

Notice how the only difference between the notes of the chords is the third. The sound and feeling of the chords are also different. It is said that the major chord sounds happy and the minor sounds sad.

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Chords in a key

To make this simpler we will just be focusing on the major scale to begin with.

There are 7 chords for each of the 7 notes in the major scale. Unfortunately it's not as simple as saying major scale = major chord. We have to build our chords from the notes available in the scale which changes things.

The following diagrams will be in the key of C major but the rules will apply to all major keys.

Let's start by numbering our notes and selecting the 1 (Root), 3 (Third) and 5 (Fifth).

Now let's count the half steps between the notes and name the intervals.

Ok. We have the root, major third and fifth. We know that one! It's a major chord :) In this case, a C major chord.

Now let's do that with the 2nd note in the scale and see what happens. Remember we only use the notes in the key, this means the 2nd note becomes our root and we count the third and fifth from there.

Now let’s count the half steps and name the intervals.

Oh this time it's the root, minor third and fifth. That’s a minor chord. In this case a D minor chord.

We do this for every note in the scale and end up with a pattern of major and minor chords.

There's also the Trey Smith of chords. The diminished chord. This chord has a minor third and diminished fifth. This means the fifth has one less half step than a perfect fifth. It’s the last chord of the major scale but it is hardly ever used so there's no need to go into further depth right now.

Every major scale follows this pattern of major minor and diminished chords so this is another one to memorise:

Major, minor, minor, major, major, minor, diminished.

Chords in a minor key

To find the chords in the minor key exactly the same way. By building our chords from the notes available in the key.

This gives us another pattern to memorise:

Minor, diminished, major, minor, minor, major, major.

Just like how the relative minor has the same notes as the relative major, it also has the same chords. Notice how the notes line up and so does the pattern of majors, minors and diminished chords.

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A Note From The Author

Before we go into our last chapter I want to take a moment to make sure you are ready.

I have done my best to explain everything in as simple and few words as possible but it is important that you fully understand each chapter so far. This means aside from what I have said needed to be memorised, you can use the information practically with little thought.

If you need to do further research elsewhere then I wholeheartedly encourage you to do so.

Depending on your instrument some lessons will be easier to implement than others, but they are all equally important to your overall understanding of music theory as a whole. None of the information has been instrument specific because music isn't instrument specific. In fact I believe one goal you should have in mind as you learn an instrument isn’t just to play that instrument, but to play music.

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The Circle of Fifths

Hopefully you’ll have noticed that a lot of the rules of music theory have been about moveable patterns. The circle of fifths takes advantage of this to the fullest extent.

At its core it's a useful tool to aid memorising keys, chords, sharps and flats but the more you understand it the more use you will get out of it.

Let’s not just memorise it however… Let’s build it!

Remember back in the chapter about keys we learned that each key has a different number of accidentals. This is what the order of the circle is based on. The outer circle signifies major keys and we put C at the top as C major contains no sharps or flats.

Sharps

Let’s start with the sharps. Every time we move up a fifth we add a sharp to the key. Let’s compare the notes of the key of C major to its fifth, G major, and its fifth, D major.

This is why we base the circle on fifths. Let’s continue moving up a fifth and filling in the first half of the outer circle.

Already we have a convenient way of knowing how many sharps are in a key. Going clockwise around the circle we add a sharp the further around we go. As we saw before, C has none, G has one, D has 2, this continues all the way down, A has 3, E has 4, B has 5, F# has 6.

There is a way to know what the sharps are too but lets fill in the other side first.

Flats

Wait a second… I thought this was the circle of fifths! Ok, let's take a little detour and connect some dots.

From the note C let’s identify the perfect fourth.

F is a perfect fourth from C. But now let's count up from F to C.

Remember that all the notes loop around and everything is made of moveable shapes. This is why we can make the diagram into a circle, it works all the way around both ways. Moving in fifths clockwise and fourths anticlockwise.

Now that's cleared up, let’s fill in the second half of our circle. Starting with F moving in fourths.

Just like the sharps, when you go anticlockwise around the circle you add a flat to the key the further around we go. F has 1 flat, B♭ has 2, E♭ has 3, A♭ has 4, D♭ has 5 and G♭ has 6.

There is also a way to know what the flats are. Let's talk about it.

The Order of Sharps and Flats

The order that the sharps and flats are added into the keys follows a familiar pattern. I’ll write them next to the keys below, see if you can figure it out.

Notice how the sharps are added in sequence, the same sequence as the circle itself starting from F. Same with the flats starting from B♭.

So there’s a bit of memorisation to the order of the circle itself but once you have done that you know how many sharps there are in a key and what they are.

There's a few more things you can do too.

4 and 5 Chords

Remember how every major key has the same order of major and minor chords?

The 4 and 5 chords are always major.

Remember how going clockwise around the circle we move a fifth and anticlockwise we move a fourth?

This means the 4 and 5 chords are directly to the left and right of each key.

Look at C major for example

Now we have the 4th and 5th chords in our key and we know they are major.

Minor Chords

By filling in the rest of the circle with the minor keys we can do a lot more.

It would make sense to start with a minor key that has no accidentals. Let’s put A minor at the top.

We can fill in all the rest following the same principals as the majors.

Notice how all the minors follow the same order as the majors except with A minor at the top. Everything then follows the same pattern.

We also have the 4 and 5 chords to the immediate left and right. Except this time, they are minor chords.

The Complete Circle

Now we have our finished circle of fifths. That's a lot to memorise in one go and there's really no need. Most music theory and instrument lessons will teach the keys by the number of sharps and flats so the easiest keys to learn are also the most common. That means you can mainly focus on memorising the top part to start with but depending on the music you want to play then understanding how the circle is made means even if you are working in an unfamiliar key you can still figure out the basics on the fly.

Here are some ways it can help you:

We know how many accidentals are in our key and what they are.

It's an easy way to know your fourth and fifth notes and chords. I’d just like to point out that the fourth and fifth chords are the same whether in major or minor. For example, the fourth and fifth of A minor are D minor and E minor. The fourth and fifth of A major are D major and E major. Knowing this will also reduce memorisation.

We now have the 6 main chords of the major and minor keys all in one box. The relative minor has the same chords as its relative major so its fourth and fifth are also in the key of the major above. (I’m not adding a whole other circle for diminished chords.)

Since everything is moveable it can help us transpose from one key to another.

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Conclusion

I hope you enjoyed learning the fundamentals of music theory with me.

There’s a lot more to learn but this should give you a solid foundation of knowledge to work from.

I’d like to point out that aside from how the notes are related and a few moveable patterns, I never gave any rules on how to make music with this information.

That's because there are none.

✨ Music is just nice sounds. ✨

If it sounds good, you’re doing something right.

Thank you very much for making it this far.

Milo