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

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

– Beibei (Singapore)

**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:

We 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:

If we play a major scale starting on the bottom note, D, we’ll discover that C-sharp is indeed in the scale. Therefore, this interval is a **major seventh**.

Now for your second question, F to E-flat:

If 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:

Here, 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.

If you join key-notes as a member, you’ll find an entire course dedicated to intervals, as this is the foundation for chords.

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