Intervals

Everyone taking grade 5 theory comes across intervals and they tend to be the point of some frustration.

But don't worry - if you just look at them the right way, they are actually fairly simple.

What is an interval? This is simply the distance or gap between two notes. So, imagine a C-Major which has these notes:

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If someone asked you the interval between C and E for example - it would be a 3rd. Why? Because "C" equates to the number "1". "D" would be "2" and "E" is "3". So 1 to 3 is a third.

The interval between D and A from the above scale is a 5th? Do you see why?

Unfortunately, it's not quite as simple as all that. You can't just say "it's a 5th". You need to also say what type of 5th it is. This is the part that usually confuses people. But if you follow this simple method, it's actually quite easy.

Imagine an accordion. If you don't know what that is, do a quick google image search.

You know how these work, you squeeze them together or pull them apart. Now, imagine you are holding one of these vertically so your right hand is at the top and your left hand is at the bottom.

Now imagine the position of your hands, holding up this squeeze box in mid air represents the interval of two notes. It doesn't matter which two notes at this stage, just imagine your hands. Now, imagine you wanted to change the length of the middle section of the box (the bit hanging between your two hands). You can do one of four things can't you:

  1. You could move your right hand up to increase the gap.
  2. You could move your right hand down, to decrease the gap.
  3. You could move your left hand up to decrease the gap.
  4. You could move your left hand down to increase the gap.

Make sense so far? So, by doing that you have taken the standard interval (I'll call it the base interval) and you've either made it bigger (augmented) by moving your right hand up or your left hand down or you've made it smaller (diminished) by moving your left hand up or your right hand down.

So - that's the first milestone out of the way. We have worked out that there is always a base interval. And something might, or might not have happened to that interval - i.e. it may have been augmented or diminished.

Have a look at this interval:

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Being presented with an interval like this can be confusing - there are lots of sharps. Some in the key signature and one against the "B". This is where the base interval comes in useful.

Now, look at that interval again and in your head, remove all of the sharps. Literally all of them, the key signature and the B#. You should be imagining this:

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Now we can see the base interval which consists of "F" and "A". If you count up (remember "F" is "1") you can see that the base interval is a 4th.

That's the first important thing out of the way. We now know that this interval is a something 4th.

Now we just need to working out what the "something" is.

Next step is to put the sharps back on the notes in your head. One thing that often helps people at this stage is to get rid of the key signature as it can be confusing. Instead, check if any of the notes in the interval appear in the key signature and imagine them with a sharp instead. In our example, the "F" is a sharp. So imagine the interval like this:

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Before we go on, let's clarify what the different types of interval are.

You can have Major, Minor, Perfect, Diminished or Augmented intervals.

Look at the C-Major scale again:

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Earlier, we said that "C" to "E" was a third. Can you see that those notes are all part of the C major scale? That makes it a major third. If you changed the "E" into an E-flat, it would no longer fit into the C-Major scale. But it would fit into the C-Minor scale. That would make it a minor third.

What about "C" to "F"? That fits into the C-Major scale and the C-Minor scale, so which one is it? NEITHER! This is what you would call a perfect interval. Perfect intervals are 4ths, 5ths and octaves (8ths). They are perfect because there is no way of telling if they are major or minor.

By this point, you should be getting a good idea of how to work out major and minor intervals. You simply start from the bottom note of the interval and see if the top note fits into the major or minor scale.

Now back to the base interval we got to earlier - here it is:

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The bottom note is F-Sharp. The top note is B-Sharp. To work out what this interval is, we start by putting ourselves in the mindset of F-Sharp Major. Go up the scale and see if you get to B-Sharp.

You don't.

So, try B-minor. No, that doesn't work either. You will find that you got to the note "B" both times which is the perfect 4th. This is where you need to imagine the accordion once more. Your left hand is at the bottom and represents F-Sharp. Your right hand is at the top and represents "B". Your hands are in the shape of a perfect 4th. Now, imagine you are adding the sharp to the "B" What would happen to your hands? Your right hand would go up a little bit. That means you've made the gap between your hands slightly bigger. You've augmented it.

It is an augmented 4th.

Do you understand why? It is a 4th that has been increased in size by a semitone. Remember this point - you could also augment an interval by increasing the gap between your hands at the bottom. Imagine your hands are now representing a "D" (bottom note) and a "G" (top note). That's a perfect 4th. If you add a flat to the "D", your left hand would go down, increasing the gap - you've still augmented it, just the other way.

That is the point where many people confuse augmented and diminished intervals.

By now, if you've understood how augmented intervals work, you might already understand diminished intervals. Look at this one:

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Follow the same process as before. You should have worked out that the base interval (strip away the flat) is a perfect 5th. Now, imagine the accordion again. Your left hand is the C at the bottom. Your right hand is the G at the top. When you add the flat to the "G" you are decreasing the gap so you are diminishing it. This makes it a diminished 5th.

It is definitely a diminished 5th, because the base interval was 5. It is not an augmented 4th, even though it would sound the same as one. It all depends on how the interval is "spelt".

That's almost all there is to it. But here is one last thing to thing to remember - a very important thing. We increased and decreased a perfect interval in our example above. This made it augmented or diminished straight away. This doesn't happen with a major interval.

Let me make it as clear as I can - this is REALLY IMPORTANT:

If you start with a major interval and increase it (from the top or bottom, doesn't matter) by a semitone, it becomes augmented.

If you start with a major interval and decrease it by a semitone, it becomes minor. Only if you decrease it by another semitone does it become diminished.

This table shows how it works if you start with a major interval (represented by "0").

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This table is for when you start with a perfect interval:

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Here are some final examples for you. I hope that's helped you to understand intervals a little better. They can be a bit tricky, but don't be put off no matter how many sharps are flats there are. Just remember to work out the base interval, then worry about what happened to it.

Pasted Graphic Major 2nd


Pasted Graphic 1 Augmented 5th

Pasted Graphic 3 Diminished 6th (the base interval is 6 and it was compressed by two semitones)

Pasted Graphic 5 Augmented 4th


Pasted Graphic 6 Major 6th