Primary Triads and Their Functions ② / Music Theory Lesson

Author: sleepfreaks

Primary Triads = The Function of the T / SD / D

Previously, we took a look at primary triads found in each major key.
These were the chords made from the tonic, subdominant, and dominant scale degrees of each key.

TSDD

Lets take a look at their degree names as well as their abbreviated alphabetical form.

TSDD_2

Keep these in mind as the true representation of the Tonic, Subdominant, and Dominant chords from this point forward.

In major keys, they are:

  • T = I, Imaj7
  • SD = IV, IVmaj7
  • D = (V), V7

The V7 is circled in yellow above because it contains the tritone mentioned in our 14th article
and thus plays a crucial role in music.

We will focus on this information in our next article, so for the time being lets learn about the function of the T and SD chords.


Making a Progression with the T and SD

If the function of the Tonic and Subdominant are to be put into words,
they can be described as written below:

  • T=Tonic

The most central chord of the key. It has a powerful sense of stability, and is often used as the first and/or last chord in a progression.

  • SD=Subdominant

It functions somewhere between the T and D chord, and adds flavor and development to a chord progression.
Moving from the T to the SD gives a sense of development and gives almost a sense of “floating” within the chord progression.
When used before the D, it creates a smooth and powerful flow when leading back to the T.

Text alone makes it difficult to get the picture, so lets give a listen to some T→SD examples.
We will be in the Key of C, so the “T”=C, Cmaj7 and the “SD”=F, Fmaj7.

※There are no rules stating that you must always start from the Tonic in music.
An SD chord can be placed first to create a different feel, and we will look at this in detail in our next article.

  • I→IV C→F

I-IV

  • Imaj7→IVmaj7 Cmaj7→Fmaj7

IM7-IVM7

  • I→IVmaj7 C→Fmaj7

I-IVM7

  • Imaj7→IV Cmaj7→F

IM7-IV

What did you think?
When it moved from the T to the SD, a sense of anticipation for where the progression will lead may have been felt.

As an experiment, lets try playing an extended F chord.

  • I→IV~~~~~ C→F~~~~~

I-IV+

It may feel like we have been expecting more but nothing is happening.
This is the sense of “flotation” that is created when moving from the T to the SD.

Now that we are floating, the laws of physics would imply that we will land.
Because of this, lets try returning back to the T.

  • I→IV→I C→F→C

I-IV-I

What did you think?
You may have felt that we returned “promptly” back to the stable feeling.

In our next article we will take a look at the last D (dominant) chord.
By using the D, you can begin to create more dramatic developments in a progression.

We will also be looking at the difference in using triads and 7th chords (4 note chords) so stay tuned!


Article Writer: Kazuma Itoh

講師 伊藤
After moving to the USA at 18 years of age with a scholarship from Berklee, he completed a 4 year study focused on song writing and arranging there.
Using this knowledge, he works across a variety of fields from pop music, film music, and more.

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