How to spot and label Secondary Dominants. Music Theory / Tonal Harmony LessonIf you’re taking a harmony course, you’ve certainly come across the concept of secondary dominants and endless exercises, where you’re given a piece of sheet music in which you have to label all the secondary dominants.

Well, today I’m going to give you a simple trick to spot and label secondary dominants. We won’t get into secondary neapolitan 6th chords or augmented 6th chords. Just secondary V and viio chords. And also, for simplicity, we will only look at pieces in major keys.

Watch this lesson in video format

Step 1: Find the key of the piece

To do that you just need to look at the key signature. If it has no accidentals, you’re in the key of C major.

If the key signature has sharps, then the key is a note a half step above the last sharp.

So, here the last sharp is a G#, and a half step above G# is A. So this piece is in the key of A major. Basically, the last sharp is the leading tone of the key.

And the last sharp in this piece, is A#. So this is in the key of B.

If the key signature has flats then the key is the second to last flat.

So here, the second to last is an Eb, then this is in Eb major.

This one is in Ab major.

If there’s only one flat, then it’s in the key of F major.

Step 2: Draw a circle of fifths in the key of the piece.

Yes! It is essential that you know the circle of fifths. It will save you tons of time when studying any music theory related topic. And to put a circle of fifths in a key, just draw the standard circle of fifths in C, and then turn it around until the note that represents the tonic of the key is at the top.

So, that is the circle in C major. Let’s say we have a piece in G major – with one sharp in the key signature. Then, all we have to do is rotate the circle counter-clockwise once, to get the G at the top, and we have a circle of fifths in the key of G major.

Or if we’re in Bb major – with two flats  – we rotate the circle yet again until the Bb is at the top. And we have a circle of fifths in the key of Bb.

Step 3: Draw a straight line from the 11 o’clock position across the circle, to the 5 o’clock position.

All the notes to the right are the diatonic notes. These are the notes of your major scale in that key. So this circle is in the key of C, and these notes are in the C major scale.

Here’s the circle in G major. So these are the notes in the G major scale.

And here’s the circle in Bb major, and these are the notes in the key of Bb.

Just make sure to use the correct accidentals. Don’t mix flats with sharps!

Step 4: Label the notes as degrees.

So, C is the I, D is the ii, E is the iii, F is the IV, G is the five, A is the vi, and B is the vii. The cool thing is that these labels are the same for every key.

In the key of G, G is the I and, D is the V and, A is the ii, and so on…

So, once you know where these labels go, you’ll never have to change them ever again.

Step 5: Write the leading tones for each diatonic note.

The leading tone is a half step below the note. So the leading tone for C is B. The leading tone for G is F#, and the leading tone for D is C#. You get the idea… And for the IV chord — the one at 11 o’clock — we’re gonna write the leading tone of the I, lowered by a half step. So, we turn the B under the C, into a Bb that goes under the F.

If the circle was in the key of G we would do the exact same thing. The leading tone for G is F#, for D is C#, and so on… And the only exception is for the IV chord. For this chord, you are always going to pair the root of this chord with the b7 of the key that you’re in. Not the leading tone! The leading tone of the IV chord is already in the key. So, it won’t show as an accidental in the score. But the b7 of the key will appear as an accidental.

So for C – the IV, at 11 o’clock – we change this F# to an F natural, lowering it by a half step. Now we have an accidental to look for, that will help us identify something that is targeting the IV.

In the key of Bb, we have an A as the leading tone for Bb then, E is the leading tone for F. Then, a B natural for C, and so on… Remember, the leading tone is always a half step below the target. And for the IV chord (Eb), we take this A, and lower it a half step to Ab.

That’s it!With this information you are ready to spot and label any secondary dominant in a piece of music.

If you come across an accidental that isn’t paired with one of your diatonic notes,you’re probably dealing with a more advanced secondary function.

So let me show you how easy it is to use this new enhanced circle of fifths.

Here I have a measure from Beethoven’s Sonata Opus 14 No.2, and the one sharp in the key signature tells me that we’re in the key of G major.

We have a couple of accidentals, and they are sharps. These are great candidates to potentially be secondary dominants. The first one is a G#. So, we look at our new and improved circle of fifths, and we look for a leading tone that’s a G#.

And of course, we find it there! G# is the leading tone to A. So this is almost certainly a secondary dominant that targets an A chord in the key of G. A is the ii in G major, so you can assume with confidence that this is going to be a secondary of ii.

Now, it could be the V/ii, or the V7/ii, or the viio/ii, or the viio7/ii. The only thing you have to do, to figure this out, is to see if the next note in the circle – moving clockwise – appears in the chord. That would be an E, in our case.

That’s because the next note in the circle is always the V of the previous note. Remember, this is the circle of fifths. So, is there an E in this chord? Yes!

So it’s either a V/ii or a V7/ii. And there’s a D. So, that means this is an E7. So this is a V7/ii. Of course, it’s an inversion, because the lowest note is not an E. It’s a G#. So we write V65/ii. 65 because G# to E is a 6th, and G# to D is a 5th.

Then we see a C#.

Probably another leading tone: C#, the leading tone to D. And D is the V. So we already know this is a secondary of V. Now, is it a viio, or is it a V? To figure it out, we look for an a the next note in the circle after D.

In other words, the V of D. If the A is there, then it’s a V of D. If it’s not, it’s a viio of D. And there it is!

An A in the bass. So this is a V of D. If there’s a G then it’s an A7 the V7. If not, then it’s a simple a triad – the V. And the G is there.

So this is an A7, which we can label with confidence as a V7/V.

In the video we show two more examples from Beethoven’s Pathetic Sonata and Chopin’s Valse Brillante.

We’ve prepared a PDF with the enhanced circle of fifths in all keys, which you can download right now if you’re an exclusive access member.

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