Subdominant and dominant !

[Mr J]

Hello everyone

I have been coming across some of the threads and books and they have been mentioning terms like subdominant and dominant.

I understand that dominant chords are characterised by a b7. What about subdominant? Please correct me if I have missed out some points!

And, how do we treat subdominant chords?

Cheers!
Jeffery

[Jakeweiser]

when people mention Subdominant and Dominant they are talking about the Function of a given harmony. It's not so much to do with what is flat or sharp, but the function of that chord and where it wants to resolve to.

Dominant chords (V) want to resolve to I, Subdom (IV) have their own strength which is a common modulation, Tonic to Subdominant via lowering the leading tone (in the key of C, the leading tone is B) by a half step (to B flat, thus modulation to F major).

Also, the Sub-Dominant acts as a cadence itself called a Plagal (the Amen) IV-I resolution which is common but not as common as V-I. Often you can find IV-V-I Cadences as well (Perfect Cadences) etc. Although I am generally rusty on most of my Classical Theory rules

In Jazz treatment of the Subdominant is often as a Lydian chord, or a chord based off the 4th mode of Major. People think of an Fmajor chord in a tune in C as a F Major7)#11) and in fact most Maj7 chords in jazz are generally automatically reharmonized to #11 chords.

All this comes from Classical Harmonic labeling of the Major scale

C - Tonic
D - Super Tonic
E - Mediant
F - SubDominant
G - Dominant
A - Sub Mediant
B - Sub Tonic/Leading Tone.

[John L]

In less technical terms, you can just think of the dominant and subdominant as chords built respectively on the 5th and the 4th notes of the of the scale in the key that you are playing, i.e if you are playing in C major, then G major (G+B+D) is the dominant and F major (F+A+C) is the subdominant.

Of course, you can add embellishments (7ths, 9ths, 11ths, 13ths etc), or substitute various notes to get different harmonic effects. As Jakeweiser notes, however, that is a different question than the definition of the dominant or subdominant.

The b7 is commonly used with the dominant because it adds tension for the resolution back to the tonic (the chord built on the note of the key that you are playing in). In jazz, the second (i.e. 9th) note in the scale of the key you are playing in is often added to the subdominant to create an alternative chord (the II7) with the same basic harmonic function.

[EdByrne]

Harmonic Clichés

Tonal music in the West is based on progressions that travel through the circle of 5ths, culminating in a cadence based upon a subdominant (active) chord to a dominant chord (most active), and resolving to a tonic chord (at rest). Subdominant is characterized by 2 and 4, dominant by the tritone (+4) interval between the leading tone and the 4th degree, and tonic characterized by scale degrees 1 and 3. Dominant is called such because it has the strongest need to resolve.

The V7 is the dominant chord in all major and minor tonal progressions. The Sub V7 (bII7) chord, however, shares the same tritone. In addition, just as there are secondary dominants, there are also secondary Sub V7s.

Below, therefore are some of the most obvious turnarounds (cadences):

ii7 (ii7-5), V7, 1MA7 (m7, m6, m69, mMA7)
ii7 (ii7-5), Sub V7 (bII7), 1MA7 (m7, m6, m69, mMA7)
bvi7, bII7, 1MA7 (m7, m6, m69, mMA7)
bvi7, V7, 1MA7 (m7, m6, m69, mMA7)

Of course, any component of a major or minor cadence can be employed in any combination, for example, ii7, V7, i7 and ii7-5, V7-9, I MA7. On the Sub V7 chords, b5 (#11) is an option.

In Tonal music, not all notes behave in the same way (have the same tendencies). In the Major scale, for example, 1, 3 and 6 of the scale are basically at rest (Tonic). 2 and 4 are active (Subdominant) and in need to move forward to dominant or resolve to Tonic. Dominant, which contains the tritone (+4th interval between the chord's 3rd and 7th (the key's leading-tone and 4th). It is usually this tritone which constitutes the Dominant function, which has the greatest need to resolve to the Tonic.

This is the basic premise upon which tonal music evolved, first creating the cadence: ii V I, in which the ii (or IV or bVII) chord is SD, the V7 chord is D, and the I is T. This cadence characterises Tonal music, since it moves from SD to D, and then resolves to T.

T: I, iii, and vi
SD: ii, IV, bVII
D: V7, vii7-5, and the Tritone Substitution, Sub V: G7=C#7

Tritone Substitutions

The Tritone Substitute (bII7-5) is used synonymously with V7. This is done both with the primary V7 and any secondary dominant. While the ubiquitous ii V I offers the strongest possible root progression (through the cycle of 5ths), the ii bII7 I presents the second strongest root progression: down in minor seconds.

The reason these two chords are so interchangeable is that they share the same tritone, the characteristic interval which creates the dominant function, since the tritone wants to resolve to tonic. For example, in the key of C Major, the F leans towards E, and the B, the leading tone, tends towards the tonic C. These notes retain the same tendencies regardless if they appear in the G7 or the Db7. Incidentally, both the G7-5 and the Db7-5 share the same four notes. They differ primarily in the aspect that D moves up a P4 (or down a P5) to the root of the T chord, while cadences involving Sub V descend chromatically. An odd symmetry of the tritone sub (when extended through the thirds to +11): Db (C#) is the #11th of a G dominant chord; G is the #11 of a Db7.

I don't think much about scales any more, but if you want a mode, it would be Lydian b7, also dubbed Lydian Dominant and the Overtone Scale: Db, Eb, F, G, Ab, Bb, Cb, Db. Having said all of this, I caution against an over-focusing on chords and scales as the primary source of improvisation, rather than the melody—or at least guide tone lines.