8,720
edits
Changes
m
→Harmonic Theory: Sub-Dominant Chord
The transition from a I chord to a IV chord involves moving the 3rd of the I chord (E) up a half step to become the root of the IV chord (F) and the 5th of the I (G) up a whole step to become the 3rd of the IV (A). This is a <u>stepwise motion</u> for a minor third interval to a major third interval. ''That means each note moves one note in the scale in the same direction.'' For example, in the key of C Major, the E and G of the I chord are a minor third. They ascend to F and A, a major third. The root of the I chord is the 5th of the IV chord, requiring no change.
The transition from IV to I is just the reverse. Stepwise motion along a scale is natural progression, in either direction. The main tension is resolving the leading tone; however, neither the I nor IV chords have the leading tone. Overall, moving from the I to IV chord creates tension, simply because we are moving away from the tonic chord. Similarly, the IV - I progression tends to reduce tension. However, the IV chord is not as tense as the V chord, and the IV - I resolution is not as strong as V - I. All of the notes of the IV chord are 1 step away from the notes of the V chord. This makes the IV chord a natural choice to progress into the V chord, giving it a <u>pre-dominant function</u> in terms of harmony. Tension increases from the I to the IV, then further from the IV to the V.
C F/C C
E--------------------------
And here is I - IV - V - I, a very basic chord progression. You can feel the tension increasing through the progression, finally relieved at the final I chord.
Notice I'm using inversions for the IV and V chord here. This is to keep the bassline rather static. When the bass jumps around too much, it's easy to focus on the bass note movement rather than the harmonic content of each chord. This is better voice leading as well.