Secondary Dominants and the Circle of Fifths

The idea

V7 pulls to I. The same trick works for any major or minor chord in the key: put its own dominant 7th in front of it. This is a secondary dominant, written V7/x and read “five of x”.

Secondary dominant	In C	Resolves to	New note it brings
V7/ii	A7	Dm	C♯
V7/iii	B7	Em	D♯ and F♯
V7/IV	C7	F	B♭
V7/V	D7	G	F♯
V7/vi	E7	Am	G♯

To find one: go up a perfect 5th from the target chord’s root and build a dominant 7th there. On guitar, that is the same fret one string lower, or two frets up on the next string.

Each secondary dominant brings a new leading tone: a note a half step below the root of the target. That is why they work. The E7 in a C major song contains G♯, which tugs up to A. This is called tonicization: treating a chord as a temporary home for a moment.

Compare the plain progression with the upgraded one:

Chains around the circle of fifths. Each dominant can resolve to another dominant: E7 – A7 – D7 – G7 – C. Every chord is the V7 of the next. This is the engine of ragtime, early jazz and many bridges. It moves counter-clockwise around the circle:

“Hey Joe” famously goes the opposite way, clockwise: C – G – D – A – E. Each chord is a 5th above the last, so nothing resolves in the usual direction. The harmony keeps climbing instead of falling home, which gives the song its restless feel.

Spotting them. Any major chord or 7th chord that “should not be in the key” and then moves to a chord a 5th below is almost certainly a secondary dominant.

On your instrument

The usual suspects on guitar:

In the key of	Look for	Which leads to
C	E or E7	Am
C	A or A7	Dm
C	D or D7	G
G	B or B7	Em
G	E or E7	Am
G	A or A7	D

All of these are open-position chords, which is one reason they are everywhere in guitar music.

Hear the leading tone. Play C – Am, then C – E7 – Am. On the top strings, follow the note G moving to G♯ and then to A. That rising half-step line is what your ear enjoys.

Piano. Play I – V7/vi – vi – V7/ii – ii – V7 – I with voice leading: each 7th resolves down by step and each leading tone resolves up.

Worked example

Upgrading a bridge. A plain bridge in C: F – F – G – G. It goes from IV to V and waits.

A traveling version, two beats per chord in the second half:

Bar	1	2	3	4
Chords	F	E7 → Am	D7	G7
Numerals	IV	V7/vi → vi	V7/V	V7

The bridge starts on IV, leans into vi through its own dominant, then uses D7 to make the arrival on G7 stronger. G7 then delivers the final chorus. Two secondary dominants turned a waiting room into a journey.

Exercises

1. Upgrade I – vi – ii – V – I to I – V7/vi – vi – V7/ii – ii – V7 – I. Play it in C and in G.
2. Find the secondary dominant in two songs from your repertoire. Use the “usual suspects” table.
3. Write a bridge that travels: start on IV, use two secondary dominants, and land on V7 ready for the final chorus.
4. Play the chain E7 – A7 – D7 – G7 – C with shell voicings. Notice that the 3rd and 7th of each chord slide down a half step to become the 7th and 3rd of the next.

Common mistakes

• Confusing a secondary dominant with a borrowed chord. A secondary dominant points at the next chord. A borrowed chord is a color in its own right. E7 going to Am is a secondary dominant. A major III chord that slides up a half step to IV, like B to C in “Creep”, is something else.
• Not resolving. The effect depends on the arrival. If V7/vi goes somewhere other than vi, make sure that is a choice.