Music Video Lesson: What are Parallel Intervals

Hi, I'm Robert Estrin and this is livingpianos.com and virtualsheetmusic.com, where the question today, what are parallel intervals? Parallel intervals. Simply put, are any intervals that go consecutively in the same direction. So for example, if you have the interval of a fifth like C to G, going to D and A, and if you continue up that way. So this is what parallel fifth sound like.

Parallel thirds would sound like this. So those are parallel intervals. What's the significance of parallel intervals anyway? Well, if you go back far enough, the very first written music was plain song or Gregorian chant. It was liturgical text, just song. Well, eventually, things evolved. It took a long time, but they've decided to have a second note, and that's when organum began. An organum was mostly parallel fourths. So what it sound was something like this, and I'll try to emulate the plain song sound a little bit, but not really not anything authentic for all you, scholars, out there just to get a feel beyond just plain notes. So that's parallel fourths more or less.

And then eventually, the strangest thing happened. As music developed into a counter points, and real polyphony, not just two notes at a time, the writings of Bach chorales and the basic rules of four-part harmony completely forbid the use of parallel fifths and parallel octaves. And you might wonder, why this forbidden? Well, there is a very good reason for it. The very first writing was vocal writing. Typically in four-part choral writing, you have soprano, alto, tenor and bass. And the idea was to have distinct separate lines that you could hear, yet, whenever the voices would sing together, would create harmony. So you have the linear element of the voices separately and together where the voices create the harmonies. And this was very interesting.

Now the reason why parallel octaves were avoided just was kind of obvious. If you have two voices singing the same note and octave apart, it sounds like the same line, doesn't it? You don't hear it distinctly as two lines. So if you're writing four-part writing and you want to hear the separate voices, obviously, you don't want to have the parallel octaves.

Well, what about fifths? Here is a thing about fifths that is very important to realize. The fifths is the first overtone after the octave. And as such, you don't really hear it as much as a separate note. So parallel fifth sounds like this, as I demonstrated earlier. You don't really hear the separate lines like you would, for example, with parallel thirds, which is a sweet sound and you'll hear the distinctness of each note because they're not as closely related in the overtone series, they really are more separate in terms of the physics of the sound. That's a very sweet sound. So parallel thirds are fair game.

Parallel fourths, if you have a chord in its first inversion, there's your C major chord. In the first inversion with the E on the bottom and a C on top, the top two notes are our fourths. So when you have parallel chords moving in the first inversion, you're going to have parallel thirds and parallel fourths, which is perfectly okay.

So if you're writing script four-part writing, you want to avoid parallel fifths and octaves or any time you want the voices to be distinct from one another. That's the long and short of parallel intervals more than you probably hoped for. I hope it's been interesting for you. Again, Robert Estrin at virtualsheetmusic.com and livingpianos.com.

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