Chords: What Are Harmonic Subdominant and Dominant Chords?
Harmonic Subdominant and Dominants are chords built by adding extra accidentals that don't exist in the original key.
How to find Harmonic Subdominants of a Major Key
In a Major key, chord IV, or the triad built on the fourth scale degree, sounds Major. For example in the key of C Major, chord IV is F Major (triad - F,A,C). By turning this triad into MINOR (F,Ab,C) we get what we call a 'harmonic' subdominant.
Chord II (i.e. chord built on the second scale degree) is also a subdominant, therefore can also be 'harmonic'. Let's say we take a seventh chord on the second scale degree (chord II7) in C Major. We have the notes D,F,A,C - which sounds like a minor seventh chord. If you alter the A to an Ab, you'll get a D half-diminished seventh chord, which is your harmonic II7!
How to find the Harmonic Dominant of a minor Key
In a minor key, chord V, or the triad built on the fifth scale degree sounds minor. For example in the key of a minor, chord V is e minor (triad - E,G,B). By altering the third to a G#, i.e. turning it into a Major triad, we get a 'harmonic' dominant. And if you add a seventh, you'll get E,G#,B,D - a Harmonic Dominant Seventh chord - which sounds like what we otherwise just know as a dominant seventh chord!
So - in a Major key, the V7 chord is a naturally occuring dominant seventh chord, but as you can see here in a minor key, the V7 dominant seventh chord is an altered chord.
How to find Harmonic Subdominants of a Major Key
In a Major key, chord IV, or the triad built on the fourth scale degree, sounds Major. For example in the key of C Major, chord IV is F Major (triad - F,A,C). By turning this triad into MINOR (F,Ab,C) we get what we call a 'harmonic' subdominant.
Chord II (i.e. chord built on the second scale degree) is also a subdominant, therefore can also be 'harmonic'. Let's say we take a seventh chord on the second scale degree (chord II7) in C Major. We have the notes D,F,A,C - which sounds like a minor seventh chord. If you alter the A to an Ab, you'll get a D half-diminished seventh chord, which is your harmonic II7!
How to find the Harmonic Dominant of a minor Key
In a minor key, chord V, or the triad built on the fifth scale degree sounds minor. For example in the key of a minor, chord V is e minor (triad - E,G,B). By altering the third to a G#, i.e. turning it into a Major triad, we get a 'harmonic' dominant. And if you add a seventh, you'll get E,G#,B,D - a Harmonic Dominant Seventh chord - which sounds like what we otherwise just know as a dominant seventh chord!
So - in a Major key, the V7 chord is a naturally occuring dominant seventh chord, but as you can see here in a minor key, the V7 dominant seventh chord is an altered chord.
