we said that this was the space between notes.

But really, to fully discover an interval, we need two pieces of information.

We, firstly, need the number of the interval, but we also need the quality.

So last week we looked at the distance between C and E.

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And we worked out that this was a third.

C to D to E.

One, two, three.

But that's only half the picture.

We say it's a third, but we need to know the quality.

We need to know what type of third is it?

Mickey, what interval is this?

>> One, two, three.

That would be a third Zach.

>> Okay. And this one?

>> One, two, three, that's also a third Zach.

>> Okay. So these

are two different intervals that we're describing as thirds.

And this is what we mean by quality.

>> Take a look at this example.

We're going to use our major scale again as the reference point.

We're going to be figuring out and

naming all our intervals with reference to the major scale.

And this will give you a set of interval descriptions that match

music theory convention.

So we're working from left to right.

If we've got two notes that are exactly the same pitch,

we say that they are in perfect unison.

The distance between the first and second, the first and

third, the first and sixth, and the first and the seventh.

Are all described as major second, third,

sixth and seventh respectively.

The distance between the first and fourth, the first and fifth, and the first and

the eighth, are called perfect fourths, and fifths and octaves, respectively.

So as we can see, in each case,

we've got a description of the quality of the interval.

And in this case, it was either major or perfect, and we also have the number,

one, two, three, four, five, six, seven, or eight.

But as we've also said, this is all based on the major scale.

So what happens if we want to work it into those that don't

belong to the major scale?

Well, firstly, we need to be aware that there are other qualities of intervals.

We've already talked about major and perfect.

We also have minor intervals, augmented intervals and diminished intervals.

>> So, let's use an example to take this forward.

On your screen, you've got a treble clef.

And a D up to a C.

The lower note is D.

The upper note is C.

So, let's count up from D: D,

E, F, G, A, B, C.

One, two, three, four, Five, six, seven.

Seven steps.

So we know we've got some sort of a seventh.

>> Okay. So

that's only have of what we need to talk about.

We've got the number now.

We know it's a seventh.

Now we need to think about the quality.

Well, a really good way to do this is to take the lowest note, and

imagine that you are in the major key.

Imagine that's the tonic of the major key.

So in this case we're going to imagine we're in the case of D Major,

because the lowest note is a D.

Okay.

So we know that in the key of D Major we've got an F# and a C#.

Therefore, the 7th degree of D Major would be C#.

This would be a major 7th.

We've already talked about this.

Actually, this is a C-natural,

which is a semitone lower than the C-sharp that we would expect in this major key.

When a major interval is made smaller,

or lowered, we say that this is a minor interval.

>> So we've now seen examples of major intervals,

perfect intervals and now we've had a minor 7th as well.

But we've also mentioned such things as augmented intervals and

diminished intervals.

So how would we get to 20 of those?

>> Well, we've seen that the unison, the fourth, and the fifth, and

the octave are described by the words perfect.

And this is the cause of the constancy between different types of scales.

So they are called perfect.

So if we have a perfect interval,

and we raise it, we make that interval bigger, we call that augmented.

And if we make that interval smaller, we call it diminished.

>> So from a perfect interval, is you step up one semitone,

you've made that interval augmented.

From a perfect interval that you make smaller by one semitone,

you've made that interval diminished.

Now, music theory convention gives us even more options if what we're starting

with is a major interval.

So if you remember, the second, the third, the sixth, and

the seventh intervals, were all originally started from our reference point.

As Major.

Major 2nd, Major 3rd, Major 6th, Major 7th.

For any of those, if you were to add one semitone to the interval,

so make the top note higher, sharpen it by one semitone.

You would immediately get to an augmented Interval.

So for major you'd step up one semi tone to augment it.

From that same major, if you were to step down one semitone, so

you were to flatten the top note by one semitone.

You would get to minor, as we'd already seen.

Now, Zach, what would happen if you were to take that minor interval and

flatten it by one semitone again?

>> Well, you're making it smaller, so

again, we can say that that interval is being diminished.

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