Music Theory Intervals

by Beibei
(Singapore)

Question: I have a question about intervals. My assignment is to write the full name of each interval:

  1. D to C-sharp?
  2. F to E-flat?
  3. B to G-sharp?
I'm very confused. Can you help me?





Albert's reply: While initially they can be among the more confusing elements of music theory, intervals are actually pretty basic once you learn a few techniques.

First, it's important to know all of your piano scales. We'll use all the major scales as references.

Second, you'll need to know how to read sheet music—at least the basics. The reason is that you can determine the interval visually, just by counting lines and spaces.

For instance, the following interval is a third, since the notes are on adjacent lines, with a single space in between:ThirdWe don't actually know which notes they are or what kind of third (major, minor, diminished, augmented), since there's no clef.

While there's a more technical, algorithmic way to determine intervals (which involves separating them into diatonic and chromatic intervals and mapping them in a matrix), I'll give you a practical shortcut. First, use the major scale as a reference. The interval between the first and second notes of a major scale (scale degrees 1 and 2) is a second; between the first and third notes is a third; between the first and fourth is a fourth, and so on.


Next, we need to look at the kind or quality of each interval. The interval between scale degrees 1 and 2 in a major scale is a major second, between scale degrees 1 and 3 is a major third, 1 and 4 is a perfect fourth, 1 and 5 is a perfect fifth, 1 and 6 is a major sixth, 1 and 7 is a major seventh, and 1 and 8 is a perfect octave.

Fourths, fifths, and octaves can't be major or minor—they're called perfect intervals for acoustic reasons.

Now let's take a look at your questions:Major seventhIf we play a major scale starting on the bottom note, D, we'll discover that C-sharp is indeed in the scale, and it's the seventh note. Therefore, this interval is a major seventh.

Now for your second question, F to E-flat:Minor seventhIf we play an F major scale, we'll discover that E-flat is not in the scale. Instead, E natural is scale degree 7. Since E-flat is one half step below E natural, instead of a major seventh we have a minor seventh. (If it were E double flat—two half-steps removed from scale degree 7—we'd have a diminished seventh.)

Finally, let's look at B to G-sharp:Major sixthHere, G-sharp is the sixth note in the B major scale. This interval is therefore a major sixth, according to my above description of intervals within the major scale.

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Music Theory Intervals

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Jun 27, 2010
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Intervals and key signatures
by: Beibei

Hi, Albert,

I have a better understanding of intervals, but I have more questions now.

Now, I know F to E-flat is a minor 7th. If I write the question (1) in the bass clef; (2) using key signatures (A-flat, B-flat, D-flat and E-flat); and (3) with two notes on F and E: In these cases, is the answer also minor 7th?

Jun 27, 2010
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Intervals and key signatures
by: Albert

Beibei,

Glad the lesson on intervals is helpful. To answer your questions, the interval is entirely independent of the key signature. To use the formula I outlined above, first identify the exact notes in the interval (following the standard rules of music notation: sharps and flats in the key signature apply to the entire measure unless cancelled by a natural sign or modified by other sharps or flats).

Then (to use my shortcut formula above) construct an imaginary major scale starting on the bottom note. If the bottom note is F, construct an F major scale. If it's E-flat, construct an E-flat major scale. Again, this is now totally independent of the key signature of the piece or section thereof.

This means that the clef also plays no role. The interval F to E-flat is the same no matter what clef is displayed. (You might wish to take a look at my How to Read Sheet Music course to really understand the critical concepts of reading music notes—I think it will significantly help you.)

As for your third question, the interval F-F (if they're on exactly the same line or space) is called a unison. Ditto for E-flat to E-flat.

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