Secondary Dominants and Borrowed Chords: Adding Colour Beyond the Key

You are playing a song in C major and every chord comes from the diatonic set — C, Dm, Em, F, G, Am, Bdim. It sounds good, but it also sounds predictable. Then a songwriter drops in an A7 chord. It is not in the key. It contains a C♯, a note that does not belong to C major at all. Yet it sounds completely natural — even exciting — because it pulls your ear powerfully toward the Dm that follows. That A7 is a secondary dominant, and it is one of the most common and effective ways to add harmonic colour without leaving the key entirely.

What Is a Secondary Dominant?

In any major key, the V chord (or V7) has a unique pull toward the I chord. In C major, G7 resolves to C. That dominant-to-tonic resolution is the strongest harmonic motion in Western music.

A secondary dominant borrows that same gravitational pull and aims it at a chord other than I. Instead of only having one dominant chord in the key, you temporarily treat another diatonic chord as if it were a local tonic and place its dominant immediately before it.

In C major, the diatonic ii chord is Dm. The dominant of D minor is A7 (because A is a fifth above D, and dominant chords are major with a minor seventh). So placing A7 before Dm gives you V7/ii — “the five-of-two.” The A7 is not in the key of C major, but it resolves so naturally to Dm that the ear accepts it without question.

Secondary Dominants for Every Diatonic Chord

You can build a secondary dominant targeting any major or minor diatonic chord (you generally do not target the diminished vii° because it is too unstable to function as a temporary tonic).

Each secondary dominant introduces one or two notes from outside the key. Those chromatic notes are what give the progression its spark — they momentarily shift the tonal centre before the music settles back into the home key.

How to Recognise Secondary Dominants

When analysing a song’s harmony, look for any major chord or dominant 7th chord that does not belong to the diatonic set. Then check: does the next chord’s root sit a perfect fifth below (or a perfect fourth above) the mystery chord? If yes, you have found a secondary dominant.

Example in C major: The progression C – E7 – Am – F.

E7 is not diatonic in C major (the diatonic iii chord is Em, not E major). The chord after E7 is Am, and E is a perfect fifth above A. So E7 = V7/vi. The E7 contains G♯, which acts as a temporary leading tone pulling up to A.

Example in G major: The progression G – D7 – G – A7 – D7 – G.

The A7 is not diatonic (the diatonic ii in G major is Am). A7 resolves to D7, and A is a fifth above D. So A7 = V7/V — the “five-of-five,” which is the most common secondary dominant in all of popular music.

Secondary Dominants in Popular Songs

Secondary dominants are everywhere once you know how to spot them.

The V7/V is the most common secondary dominant in all of popular music. Any time a songwriter wants extra push toward the V chord, V7/V is the go-to move — it appears constantly in country, folk, and classic rock.

The V7/vi gives songs an emotional lift. In C major, the progression C – E7 – Am – F powers countless pop and rock songs by adding G♯ as a chromatic leading tone before Am.

The V7/IV is a blues staple. When a song in C adds B♭ to the C chord (making it C7), that B♭ pulls the ear toward F — the sound of the I-to-IV move in a 12-bar blues.

What Are Borrowed Chords?

While secondary dominants create chromatic colour by targeting diatonic chords, borrowed chords bring in entire chords from a parallel key. This technique is also called modal interchange.

The parallel key shares the same root but uses a different scale. The parallel minor of C major is C minor. Both keys have C as their tonic, but they use different sets of notes and therefore different diatonic chords.

Borrowing means taking a chord from the parallel minor and using it in a major-key context (or vice versa). The most commonly borrowed chords in major keys are:

Borrowed Chords in Action

The iv chord is perhaps the most emotionally effective borrowed chord. In C major, replacing the diatonic F major (IV) with F minor (iv) turns a bright chord into a shadowed one. The note that changes is A (in F major) becoming A♭ (in F minor) — a single half-step drop that transforms the mood. Radiohead’s “Creep” uses this device: G – B – C – Cm. That final Cm is iv borrowed from the parallel minor, and it is the moment the verse turns from tension into despair.

The ♭VII chord gives rock and pop a grounded, modal quality. In C major, B♭ borrows from C Mixolydian or C minor and creates a satisfying plagal-like motion resolving to I — the ♭VII – I ending that powers countless rock anthems.

The ♭VI chord is the tool of choice for cinematic drama. In C major, A♭ introduces both A♭ and E♭ — two foreign notes — creating a sudden colour shift. The progression I – ♭VI – ♭VII – I (C – A♭ – B♭ – C) is a film music and epic rock staple.

Combining Secondary Dominants and Borrowed Chords

The two techniques are not mutually exclusive. Skilled songwriters layer them for maximum harmonic interest.

Example progression in C major: C – E7 – Am – Fm – C

This uses V7/vi (E7) to intensify the arrival on Am, then pivots to a borrowed iv (Fm) for an unexpected emotional turn before resolving home to C. The E7 looks forward, the Fm looks back, and the C provides resolution. Three chords, two chromatic techniques, one seamless phrase.

To explore how these chords relate to the diatonic set, open the Interactive Chord Finder and select C and the Major scale. The Diatonic Chords table shows you the standard seven chords. Then switch to C Natural Minor to see the chords available for borrowing. Comparing the two tables side by side reveals exactly which chords can be borrowed and which notes change.

Tips for Using These Techniques

Use secondary dominants to strengthen motion toward an important chord. If your chorus starts on the vi chord, placing V7/vi at the end of the pre-chorus creates a strong arrival.

Use borrowed chords for emotional contrast. A major-key verse with a single borrowed iv or ♭VI in the chorus can transform the mood without a full key change.

Do not overuse either technique. One or two chromatic chords per section is usually enough. The power of these devices comes from contrast — if every chord is chromatic, nothing stands out.

Trust your ear. Theory explains why these chords work, but you should choose them because they sound right, not because a textbook says so.

Where to Go from Here

Secondary dominants and borrowed chords are the natural next step after mastering diatonic chords and chord progressions. They open the door to more advanced topics like tritone substitutions, chromatic mediants, and modulation — techniques that take harmonic colour even further. For a practical framework to identify these devices in music you listen to, the harmonic analysis guide walks you through the process step by step.

Start simple: take a progression you already play, pick one chord, and replace it with a secondary dominant targeting the next chord. Hear how that single change adds momentum and colour. That is the beginning of thinking like a composer.