So now let's turn to some of the puzzles in scales. And the first of these puzzles is, why are a relatively small number of scales used? So I mentioned the C major scale, and here are some other examples of scales that are used, again, not just in Western music, but in music worldwide or at least in musical traditions that have come from different historical sources altogether. So, I mean, this always raises the fundamental point of the universality of music. And my view is that the universality of it is really striking and demands an explanation. So here are some examples of the five and seven interval scales or modes that have been used. These pentatonic scales are five-interval scales, again, six notes, five intervals. Heptatonic scales are seven intervals or eight notes. Heptatonic scales are also called diatonic scales. This is a term you'll hear, diatonic. I'll just write it down here since it's not written. That's just a rubric that basically covers the commonly used seven-note scales. So these scales have names. We talked about the major scale in the last lesson, but there are a whole bunch of others, and they all have names. The names are historical, stemming from the so-called Greek modes that were used in ancient Greece, again I emphasize that this was not Pythagorean at all. So these names, Ionian, Aeolian, Dorian, Phrygian, Lydian Mixolydian, Locrian, those are all Greek words that are historically used to define the seven-note scales and what differentiates them, or the five note scales are differentiated in the same way, which differentiates these scales. Each one of which is being indicated by the red dots on the piano keyboard. Again, piano keyboards are all the same, starting on C. What differentiates these scales is the arrangement of their order. How many, they're all either five intervals or seven intervals, but the order, you'll notice, is very different. And the order is what gives them their different character, their different names. And the question that I'm focused on in this lesson, that's certainly just one of many questions that all this raises, is why are there a relatively small number of these? If you think about the way in which we can differentiate pitches over an octave, the observation that's been repeated many times is that it just takes a frequency change of 3 or 4 hertz to enable us to discriminate a different pitch. So we can discriminate depending on where we are over the range of hearing. We can discriminate something like 200 or more different intervals over an octave. So why limit the notes in an octave to intervals that are five or seven in the scales that are commonly used? Why is this? Why just these few intervals? And if you look at scales that are used worldwide, there are really only about, estimates would vary a lot depending on who you talk to, but there are only in the order of a few dozen scales that are commonly used worldwide. And these that are shown here are ones that really bring out the sort of major ones that are used in various genres of music today. And the vast majority of western popular music is using the major scale and the minor scale, the heptatonic major or the natural minor, or some other variation of the minor scale. Those are the scales that are common in Western music. In folk music, which emphasizes only the more consonant intervals of the chromatic superset that I talked about in the last lesson, folk music emphasizes those, whether it's Western or other, folk music tends to be in a pentatonic scale. So in general, if you think about the difference between a pentatonic scale and heptatonic scale, the fewer the number of notes, the more you can emphasize consonant notes. And I should say again, that Scales are not dictatorial in a sense that if you're playing in a given scale you can only use those notes, no, far from it. These are simply the notes that are emphasized in a composition in whatever scale the music happened to be composed are being played in, it's not in any sense mandating that you play only those notes. So again, I think it's useful to hear what these scales sound like, the differences between them, and let's turn to Ruby's examples here and listen to some of these scales. [MUSIC]
