# The dominant chord rules!



## millionrainbows (Jun 23, 2012)

The only way to understand this is to hear it, so get a beer, go to your Bosendörfer Imperial Grand, and try this:

"Dominant" refers to the function of a chord, it tendencies, and what it "wants" to do. In any major scale, each note is a possible root from which to build a triad. The seven note functions are represented with Roman numerals. Capital numerals denote major; small numerals denote minor (or diminished on vii). The functions are: I (tonic), ii (supertonic), iii (mediant), IV (subdominant), V (dominant), vi (submediant), and vii (leading tone).

These functions change in minor keys & other scales. There are function-names for every chromatic note, not just the seven diatonic (within the key) ones above; for example, flatted submediant, etc.

A "dominant" chord is a "V" chord; any chord with a major third and a flat-seven. This interval is a tritone. It is the symmetrical mid-point of the 12-note chromatic scale. For example, in the octave from C to C, C-F# and F#-C are the tritones. This interval is symmetrically invertible; i.e. when you invert it, it is still a tritone, unlike the other intervals (except the octave). Inverted major thirds become minor sixths, etc.

Here's where "function" comes into play. The root determines the function of the notes in the tritone. 

If the tritone is occupying the notes F-B, and the root is G, then F is the b7 and B is the third. The F wants to resolve down to E, and the B wants to resolve up to C, making it a V-I cadence in C. This is the typical V-I progression.

Alternately, if the root is C#, then the functions (3-b7/b7-3) are reversed: F (called E# in the key of C#) is the major third, and B is the b7. The tritone can be resolved to F#: F down to E (b7), and B down to Bb (or A# in the key of F#), the major third.

Getting complicated, isn't it? If we combine these root movements, we see other possibilities emerge: play F-B in your RH. All these will resolve F down to E, and B down to Bb.
The possible root movements are: G-C; G-Gb; C#-F#; and C#-C. So you see, we get two different V-Is, and two different chromatic half-step resolutions, all out of one tritone relation.

After playing with this, you begin to see that a series or cycle of V-Is is similar to a chromatic movement. Both cycles will eventually exhaust all twelve notes; the V-Is do it by fifths, and the chromatics do it in succession.

The be-bop jazz players exploited this characteristic of dominants & tritones, calling it "tritone substitution." Jazz is mostly cycles of V-Is, so instead of G7-C7, they would substitute a new root and go C#7-C7, or G7-F#7. 
Try this as an endless cycle or loop: G-F-B to F#-E-Bb; C-E-Bb to B-Eb-A; F-Eb-A to E-D-G#; Bb-D-G# to etc. 
Notice the I-Ching hexagram-like transition? The last two notes of each second group are carried over to the next first group: E-Bb/Eb-A/D-G#, etc.

The Second Viennese School used this chord (see the New Grove "Second Viennese School"). The chord is (low to high): Bb-D-E-Ab, which, if shifted down one semitone to A-C#-D#-G, is equivalent to the same chord transposed a perfect fifth down: Bb-D-E-Ab to Eb-G-A-Db, which are the same notes (Eb=D#, G, A, Db=C#). This illustrates what I was talking about above, the "chromatic-fifths connection."


----------

