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  • In this lesson I’m going to talk a little bit more about perfect intervals.

  • Now that you already know how to spell thirds and invert them

  • the remaining intervals are going to be a lot easier to learn.

  • Perfect intervals, abbreviated with a P, are going to include fourths,

  • and fifths, and octaves, and I’ll even put this one down.

  • A one would be a unison. I can’t play that one the piano

  • because it’s the same note played twice so you need two different instruments to create unison.

  • But it’s also considered perfect.

  • First I’m just going to make a fourth, like this, and you might notice that

  • it goes from a line to a space when you write a fourth,

  • or it could be like this, from a space to a line.

  • They have a really characteristic look on the staff.

  • This first one, I’m going to keep the C where it is and I’m going to

  • wrap the G around it and put it in the other octave, like that.

  • And then I can just take that away. So I had that fourth and I inverted it into a fifth.

  • So of course, 4 + 5 = 9, and we know that when we invert intervals we get nine.

  • But what about the perfect part? It was perfect fourth and perfect fifth.

  • It turns out that if something is perfect and you invert it, it is still perfect, so that’s easy to remember.

  • So, perfect equals perfect when you invert it.

  • Now let’s try a couple others that might involve some accidentals.

  • Were just going to notate a couple of intervals here.

  • Were going to start with a perfect fourth up, like this.

  • So with this one, you can kind of think back about major thirds.

  • Major thirds are just one half step smaller than perfect fourths.

  • That means that if major thirds have four half steps, then perfect fourths must have five.

  • That also tells you that if you invert a perfect fourth, that’s five half steps,

  • youre going to get something with seven half steps because seven and five is twelve.

  • With four half steps, sometimes people have all kinds of tricks for this.

  • If you happen to know that F to A is a major third, you could just go up a half step,

  • like this, a half step up from A is B flat, and that’s going to give you a perfect fourth.

  • That's one way you can do it. But, you can also do it another way.

  • You can count, F, G, A, B. So you know it's some kind of a B,

  • and then you have to check how many half steps you have.

  • So let's look at the piano. We've got our F, and then one, two, three, four.

  • So if we just left the notes as they are, we'd get this sound.

  • Now your ear might tell you that this is a really harsh sound, it doesn't sound like a perfect interval.

  • That alone could tell you that something is wrong.

  • Now we're going to go the way I first showed you.

  • Let's say you happen to know F to A is your major third. I'm going to raise that up half a step.

  • F to B flat gives me my perfect fourth.

  • And then we can count. One, two, three, four, five. And there's the five half steps.

  • We're going to look back up here and try a couple more.

  • So I'm going to put my flat right here. There's my perfect fourth.

  • Let's do a fifth. How about this one? We'll do a perfect fifth up

  • We can start by counting. That gives me a C. Some kind of a C.

  • Now, when I play this on the piano, it's going to sound very very dissonant.

  • The nice thing about fifths, is two things. First of all, if one note is on a space, the other one will also be on a space.

  • If one is on a line, the other one will be on a line.

  • You'll get to know how they look, just like you know the way fourths look.

  • I know I have them on the right place in general, but I'm just not sure about the accidentals.

  • Well the other nice thing about perfect fifths is that they're usually going to have the same accidental.

  • But not always, so we'll look at an example where that's not true.

  • Usually they're going to have the same accidental.

  • Now if you want to verify this to make sure this is actually right, there are a couple ways you can do it.

  • Back over here on the keyboard, I had F sharp and the first thing I wrote was just a C.

  • That's that really dissonant sound.

  • F sharp to just a C natural. That's way too dissonant for a perfect interval.

  • Then I thought they usually have the same accidental in front of them, right?

  • F sharp to C sharp. Now we can count, one, two, three, four, five, six, seven.

  • Seven half steps, and I know that has to be true because a perfect fourth has five

  • five plus seven is twelve. Let's look at it in one more way.

  • I'm going to invert this and make sure that it inverts to a perfect fourth.

  • I'm going to keep my F sharp the way it is,

  • and I'm going to take that C sharp and move it down to the previous octave.

  • That sounds like a perfect fourth, but I want to make sure.

  • One, two, three, four, five. Five half steps.

  • I'd rather count five half steps than seven half steps.

  • So if I'm going to count, I'm going to count the inverted interval,

  • and then invert it back to where it was.

  • We're going to look at an example where a perfect fifth doesn't have the same accidental

  • kind of like the perfect fourth over here,with two different accidentals.

  • Let's try this one.

  • Now I'm going to try to write a perfect fifth down from F.

  • It turns out that when you're writing fourths or fifths, and you're using these notes F and B,

  • you tend to get some funny things that happen.

  • The reason for that is that the keyboard is not symmetrical.

  • There are, as you remember on the white keys of the piano, there are half steps between

  • B an C, and E and F, and all the other ones have whole steps.

  • That means that even though something might be true in one case, like the two sharps here,

  • it's not going to be true in every case, because the keyboard is not symmetrical.

  • Let's look and see what happens here.

  • I know they're both supposed to be on the line, because that's how perfect fifths look,

  • so instead of counting, I can just go like this. Skip that line in the middle.

  • I can always count if I need to verify if that's a fifth, but I know that it is.

  • Now this one has got a B and an F in it, so when I play it on the keyboard,

  • because I know about the keyboard, I know it's going to sound really dissonant.

  • Let's see if that's true.

  • Here's the F, and if I walk down, one, two, three, four, five,

  • there it is. So this is not a perfect fifth. It's very dissonant sounding.

In this lesson I’m going to talk a little bit more about perfect intervals.

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A2 初級

音樂101:完美的間奏 (Music 101: Perfect Intervals)

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    songwen8778 發佈於 2021 年 01 月 14 日
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