Applied Chords Ref Sheet

Published: Aug 5, 2026 by Courtney Rosenthal

This is my 3rd blog post for the Blaugust 2026 community blogging project. Join me all this month for more blogging.

I’m now in my third term of music theory. Back in the first term, I created a handy reference sheet for major and minor scales. I just added a new ref sheet for what’s called applied (or secondary) chords.

A Bit of Music Theory

(If you know basic music theory, go ahead and skip this part.)

First, listen to this music snippet:

Here is the music score for what you just heard:

A staff of music notation in treble clef and 4/4 time showing three whole-note triads, labeled with the chord symbols C, F, and G above the staff and the Roman numerals I, IV, and V below. The line closes with a final double barline. (Description assisted by Claude AI.)

If you enumerate the C major scale – C-D-E-F-G-A-B – you see that C is the first note. The chord built on top of it is a C major chord, and is denoted by roman numeral I. Similarly, F is the fourth note on the scale. The chord built on it is an F major chord, and is denoted by roman numeral IV. And the final chord in the sequence is the V chord, a G major chord.

This sequence is the I-IV-V chords in the major scale. You’ve heard this a zillion times.

So, what comes next in the song? Probably a C major chord. Your ear really, really wants to hear this resolve back to a C major chord. Listen again and tell me if that’s not true!

In music theory, we say that the V chord in a major scale is a dominant chord, because it wants to resolve back to the I, called the tonic chord.

Now, let’s make one teeny change to the song: we’ll add one chord to the sequence. Listen to this:

Here is the music score for that snippet:

A staff of music notation in treble clef and 4/4 time showing four whole-note triads, labeled with the chord symbols C, F, D, and G above the staff and the Roman numerals I, IV, V/V, and V below. The third chord carries a sharp on its third. (Description assisted by Claude AI.)

Whoa! Remember how in the first snippet the G major chord wanted to resolve to the C major chord really badly? But here, in this second snippet, the song wouldn’t mind hanging out for a bit on that same G major chord. And who knows where it will go after that?

That added chord is a D chord, and it’s called a secondary dominant chord. It greatly changes the character of the G major chord that follows. It makes it a temporary tonic – a stable, resting place – in the song.

You get a secondary dominant chord by building a chord on the 5th degree above the target. In this case, the target is G major. So the secondary dominant of G major is: G-A-B-C-D … the D major chord.

Applied Chords Ref Sheet

That’s just one example of how secondary dominant chords can be used.

Secondary dominant chords are part of a class of chords called applied chords (or secondary chords) that let you “tonicize” any chord in the key. There are a number of options, across major and minor musical scales.

I created a reference sheet to help identify and construct these chords. Here it is:

You can download a copy from here: pub.crosenthal.com/music-theory-refs/applied_chords.pdf

The project that generates my music theory reference sheets is open source. The code is posted here: codeberg.org/crosenthal/music-theory-refs

If music theory is your thing, I’d love to hear your feedback.

Enjoy!