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Video Transcription
Hi, I'm Robert Estrin, this is LivingPianos.com, your online piano store, and you probably clicked on this because you thought it was either a mistake, 3 plus 3 equals 5, or you thought I'd lost my mind. Well, believe it or not, it's neither one of those. I'm going to show you how 3 plus 3 equals 5 in certain circumstances, and how this can possibly be.
You know, recently I did a video on what is a triad. A triad is the building block of Western music. It's a chord containing three notes arranged in thirds, and you have two thirds, a third on the bottom, and a third on the top. So, here's a triad.
We have a third on the bottom, there's one third, and there's the other third, 3 and 3.
And yet, the outer interval is a fifth. One, two, three, four, five. A root, a third, and a fifth. How can two thirds equal a fifth? Did you ever think about this? Now, many of you will probably know instantly what the answer to this is, but I thought it was an interesting thing to ponder. How you can build a chord out of two thirds, and end up with a fifth, because that doesn't make mathematical sense. Well, the reason is that the bottom third, and the top third share the same note. It's as simple as that. One, two, three, four, five. So you have a root, a third, and a fifth, which is comprised of a third on the bottom, and a third on the top.
And that's the simple mathematics of it. So, three plus three equals a fifth in triads, but the math is still right, so don't worry about it. Don't trade in your calculator, or rack your brains over this any further. I hope this is clear. If any of you still have questions about this, put them in the comments here at livingpiatos .com and YouTube. And if you have any other theory questions to address in future videos, I am here for you. Robert Estrin at LivingPianos.com. Thanks so much for joining me.
Hi, Robert. You are definitely right to have pointed out that the third of, say, a C major triad is counted twice in the 3+3 consideration. If we go deeper into it, this double counting has originated from the way any interval is counted to get the span-related part of its name, i.e. we do not count the number of big or small steps to go, but count the beginning note, the ending note & other diatonic notes in between, so going from note C to note E is called an interval of major third, just as going from note E to note G is called an interval of minor third, where it is obvious that note E is counted twice when these two intervals are combined to form the C major chord, which is then called an interval of perfect fifth when note E is no longer counted twice.