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.


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


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


  • Imaj7→IVmaj7 Cmaj7→Fmaj7


  • I→IVmaj7 C→Fmaj7


  • Imaj7→IV Cmaj7→F


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~~~~~


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


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.