So last week we talked about intervals, and we said that this was the space between notes, but really to fully describe 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 to the distance between C and E. [MUSIC] Everyone will tell you that this was a third, C to D to E, one, two, three. But, that's only half the picture We say it is a third, but we need to know the quality, we need to know what type of a 3rd is it? Okay so [FOREIGN]. >> One, two, three. That, that'd be a 3rd, Zack >> Okay and this one? [MUSIC] >> One, two, three. That, that's also a 3rd, Zack. >> Okay, so these are- [MUSIC] two different intervals that we're describing as 3rds 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're in perfect unison. The distance between the 1st and 2nd, the 1st and 3rd, the 1st and 6th, and the 1st and 7th are all described as major. 2nd, 3rd, 6th, and 7ths, respectively. The distance between the 1st and 4th, the 1st and 5th, and the 1st and the 8th are called perfect 4ths, and 5ths, and octaves, respectively. These intervals would all be the same in a major or a minor key. Hence, perfect. >> So as you 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 1, 2, 3, 4, 5, 6, 7, or 8, but as we've also said, this is all based on the major scale. So, what happens if we want to work at intervals that don't belong to the major scale? Well, firstly, we need to be aware that there are other qualities of intervals. So, 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 7th. >> Okay, so that's only half of what we need to talk about. We've got the number now, we know it's a 7th. 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 Sharp and a C Sharp. Therefore the 7th degree of D Major, would be C Sharp. 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, it's smaller, or lowered, we say that this is a minor interval. >> So we've now seen examples of major intervals, perfect intervals and, and now we've had our minor 7th as well. But we've also mentioned there's such things as augmented intervals and diminished intervals. So, how would we get to any of those? >> Well, we've seen that the unison the 4th, and the 5th, and the octave, are described by the word perfect. This is because of the constancy between different types of scales. So they're called perfect. But 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, if 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 given us, gives us even more options if what we're starting with is, is a major interval. So if you remember the 2nd, the 3rd, the 6th, and the 7th, intervals, what 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 setup one semitone to augmented. From that same major if you were to step down one semitone. So if you were to flatten the top note by one semitone, you would get to minor as we'd already seen. Now Zack, 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 see that, that interval has been diminished. [BLANK_AUDIO]
