A musical interval is just a unit of measurement between two pitches,

and we can use numbers to show the relative distance between these pitches.

If we’re talking about something like a perfect fifth, which sounds like this,

I’m just going to show you with my hands.

Say this was here, then I want to do a third, it would be narrower, like this.

Then if I wanted to do a bigger number,

the distance between the pitches would get bigger too.

It’s just a unit of measurement and of course the keyboard works great

to think about intervals because you can see how far apart the piano keys are.

let’s say that we wanted to write an E, and we want to do a perfect fifth up from E.

This is really easy, because all you have to do is count through the alphabet.

Here’s the perfect fifth up, and we’re just going to count like this:

start with E, so there’s E, F, G, A, B.

That’s five, so we’ll want to write a five.

So I’m just going to go like this: one, two, three, four, and there it is.

That’s a fifth, and this P I have in front of it is a little more information that helps

describe the sound to me, and we’ll talk about that a little bit later.

So let’s try another interval, and then we’ll see what they sound like.

Let’s go to treble clef this time, and we’re going to do a third.

Let’s do a third down from this. I’m just going to do three down.

Again, all you have to do is count, and there are two ways you can count.

You can count down like this: one, two, three, and you know the other note has to be here.

Or, you can count down in the alphabet, so G, F, E, so you know it has to be an E.

So it’s really just counting. And we’re going to do one more.

Let’s see, this one is going to be a seventh.

We’re going to go from here, and this is going to be a seventh up.

So from C – again, you always start counting with the one that you’re on right here –

so C, D, E, F, G, A, B. That must be a seventh. Or you can count like this.

That’s how you notate those intervals, and we’re going to see what those sound like on the keyboard.

The first one was a fifth, and it was up from this E down here.

That’s a fifth, and the next one I had a third, which sounds like this.

And then I had a seventh. Like that.

You might notice these all sound a little bit different.

I’m going to go back to that first one I played where I had that P in front of it

and I said it was a perfect fifth.

The general category of these types of intervals that I’m playing right now

that general category is called perfect.

they have kind of bell like sounds, kind of clear, you might hear that a lot of the

orchestral strings are tuned in fifths when they tune their instruments.

And so the general category for fifths and fourths and octaves is called perfect.

We’re going to go to the next category.

This is a third, and you can see it easily on the keyboard because one, two, three.

This is a sixth. It turns out that thirds and sixths are both in the same category too.

I’ll play a few more of those. These are all thirds.

And then here are a few sixths. Like that.

The general name for all these kinds of intervals is called consonant.

And there’s one more category, and it’s called dissonant.

We were looking at fourths and fifths and octaves as being perfect,

but there’s something called a tritone that's in between a fourth and a fifth that's considered dissonant.

If you want to write one of these intervals, cause they sound kind of neat, you can do two things.

You can either make a fifth and shrink it, or you can make a fourth and make it bigger.

This is a fourth, and what I’m going to do is use an accidental to make it a bit bigger.

I’m going to make it a half step bigger.

So I could do it a couple different ways.

I could put a sharp here, and that would work really well.

Or, I could go back over here and I could put a flat there.

Either way I have this interval. I could raise the top or lower the bottom.

And then I can do the same type of thing with a fifth.

I can make a fourth bigger or a fifth smaller to make a tritone. So we’ll just do that.

So here’s a fifth, and I’m going to raise the bottom up to make it a little smaller.

Of course I could also do that. I’m going to play with what these sound like on the keyboard.

So here’s that fourth that I played, and that I notated.

And you can see that it’s very clear sounding, it’s perfect,

category of perfect intervals, but now I’m going to lower that G.

It changes the sound and now it’s dissonant. Or I could do it the other way.

Raise the C. Very dissonant.

I’m going to do the same thing with that perfect fifth.

Here’s that fifth, very clear, very bell like.

But if I raise the bottom of it, all of a sudden, it’s dissonant.

Same thing by lowering the top.

And that’s all the lesson for now.