Secondary and Applied Chords (Secondary Dominants)
Secondary chords (sometimes called applied chords) are a category of chords used to momentarily emphasize a chord other than the home base I chord as a new tonal center. The strongest way to make our ears hear a chord as home base is to play the V of that target chord followed by the chord itself (see cadence). This means that the most common secondary chords function as the “V of” the desired new home base target chord.
For example, if a song wants to briefly make the ii chord sound like the home base chord instead of I, the secondary chord that is the “V of” the ii will be played (often followed by ii itself). In the key of C major, the D minor chord is the ii chord. If this D were the home base I chord, the V chord of D would be an A major chord, so A major is the “V of ii” in C. In Roman numeral notation, “V of ii” is written “V/ii.”
ABBA’s “I Do, I Do, I Do, I Do” is a song that makes prominent use of a V/ii chord. Notice how the V/ii resolves back to the ii.
This V/ii chord, or A major in the key of C, contains the notes A, C♯, and E. Notice that C♯ is not in the C major scale. C is scale degree 1, so C♯ would be written 1♯. By incorporating non-diatonic notes outside the original key, these secondary chords introduce a heightened sense of tension and resolution, adding variety and complexity.
In the song above, we also see these non-diatonic notes appear in the melody. The C♯ in the V/ii also appears in the melody, giving it more emphasis. It is the orange and red hashed note that is colored that way because it is between scale degrees 1 and 2 (C♯, the black note between C and D on the piano).
The chords we have discussed so far all involve a V and are known as secondary dominants (dominant is another word for V due to its important relationship to the home base and in cadences). While secondary dominants are particularly common and powerful due to the V chord’s natural resolution tendencies, other forms of secondary chords are possible, with common examples functioning as the “IV of” or “vii˚ of” a temporary home base.
John Mayer’s “Who Says” makes several uses of secondary chords, including the very common secondary dominant V/V (a D major chord in the key of C major resolving to G) as well as a “vii˚ of vi” going to vi.
Other songs that use secondary chords
Click on the following songs to see their chords and melody in the TheoryTab database.
