• # Who Else Wants To Know Why Compound Intervals Cannot Be Inverted?

in Piano

You arrived at this page because you’re interested in knowing why compound intervals cannot be inverted.

However, there are those who don’t know how intervals are classified into simple and compound. Therefore, we’ll be starting out in the next segment by looking at simple and compound intervals.

Let’s get started right away.

## On Intervals: Simple Vs Compound Intervals

The relationship between two notes that are heard (together or separately) produces an interval. The following note relationships are intervallic:

C and E:

D and Ab:

A and F#:

…etc.

Although there are so many ways to classify an interval, interval can be classified either as simple intervals or compound intervals.

Check them out!

### A Short Note On Simple Intervals

Simple intervals are intervals that are smaller than or equal to the octave. Intervals from the unison (which is also called the first) to the octave are all classified as simple intervals.

“Let’s Check Out Examples Of Simple Intervals…”

Attention: Keep in mind that we’re using the key of C major as our reference.

C-C:

…which is the unison.

C-D:

…the second.

C-E:

…the third.

C-F:

…the fourth.

C-G:

…the fifth.

C-A:

…the sixth.

C-B:

…the seventh.

C-C:

…the octave or eighth.

## “Here’s Why Compound Intervals Cannot Be Inverted…”

Before I tell you why compound intervals cannot be inverted, permit me to prepare your mind with a short study on the relationship between the concept of inversion and the octave.

Understanding this relationship will deepen your understanding of what I’m about to show you.

### The Relationship Between The Concept Of Inversion And The Octave

When a  given interval and its inversion are summed up, the product is an octave.

For example, C-E and its inversion are given below:

C-E

E-C:

When summed up, both intervals produce the octave:

C-E + E-C:

…produces the octave (C-C):

“Let’s Take Another Example…”

The inversion of A-E produces:

A-E:

E-A:

If you go ahead and sum both intervals together:

A-E + E-A:

…produces the octave (A-A):

Attention: This is strictly accurate for all intervals that are smaller than or equal to the octave.

### Compound Intervals Are Bigger Than Any Octave

The smallest compound interval in tonal music — which is the ninth — is bigger than the octave. Using the key of C major (as a reference):

…the smallest ninth intervals are the minor ninth and major ninth:

C-Db (minor ninth):

C-D (major ninth):

…and both intervals are bigger than the octave (C-C):

### “Can I Tell You Why Compound Intervals Cannot Be Inverted?”

Due to the relationship between the concept of inversion and the octave, only intervals that are smaller than or equal to the octave can be inverted.

When a given interval is inverted, the given interval and the inversion produce the octave when put together.

For example, if it were possible to add the ninth interval with another interval to produce an octave, then it would have been possible to invert a ninth interval. Meanwhile a compound interval (like the ninth) is bigger than the octave itself.

So, compound intervals like the ninth, tenth, eleventh, twelfth, thirteenth, and fourteenth cannot be inverted because they exceed the compass of an octave.

## Final Word

One of the significant differences between simple and compound intervals is inversion.

So, it’s safe to say that simple intervals are intervals that can be inverted while compound intervals are intervals that cannot be inverted.

In a subsequent lesson, we’ll explore two classes of compound intervals and what you need to know about them while studying harmony.

See you then.

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#### Chuku Onyemachi

Head of Education at HearandPlay Music Group
Onyemachi "Onye" Chuku (aka - "Dr. Pokey") is a Nigerian musicologist, pianist, and author. Inspired by his role model (Jermaine Griggs) who has become his mentor, what he started off as teaching musicians in his Aba-Nigeria neighborhood in April 2005 eventually morphed into an international career that has helped hundreds of thousands of musicians all around the world. Onye lives in Dubai and is currently the Head of Education at HearandPlay Music Group and the music consultant of the Gospel Music Training Center, all in California, USA.