Thoughts on Modes
It's my opinion that thinking of a mode in terms of its "parent" mode is counter-productive. In other words, I don't think of "D dorian" as having any relationship at all to "C major". In my mind they are completely distinct and unique entities, with different tendencies, different harmonies and a completely different feel.
For me, thinking of "D dorian" as a "mode" of "C major" is one step too many in the visualization process. The fact that they both have the same notes in common, I prefer to think of as a "coincidence".
For example, to me thinking of "G mixolydian" as the mode built off the 5th degree of the "C ionian" is just as silly as thinking of "C ionian" as the mode built off the 4th degree of the "G mixolydian".
Thinking of modes in relation to their "parent" scales becomes even more convoluted when dealing with modes built off melodic minors, harmonic minors and artifical scales. It's better not to have to go the extra step - ie. Don't think of "F lydian dominant" as the 4th mode of "C melodic minor ascending". Just think of it as "F lydian dominant"!
However, when soloing over a progression like this, most people will simply "visualize" that they're playing the C major scale over these changes and avoid the extra brainwork involved to "name" the various modes as they cycle through.
2. The other way modes are used are as unique tonal centers. The point that most seem to miss when dealing with modes is that the tendencies and harmonic progressions are completely different than those of their major or minor "relatives".
The function of a "dominant chord" is to propel you into the tonic. The dominanting chord of the ionian is the chord built off the 5th degree ("dominant V chord"). This is not true for the other modes when used as tonal centers:
- D dorian has as its dominating cadential chord a G7 (IV7). (Many Santana songs are good example of this).
- E phygrian has as its dominant chord an F major chord (bIImaj). This mode is often called the "Spanish minor".
- F lydian generally uses the G major triad (II).
- G mixolydian has as its dominant functioning chord F major (bVIImaj). (The Beatles' "Norwegian Wood", Eric Clapton's "Cocaine", and the Grateful Dead's "China Cat" are all good examples of mixolydian songs).
- A aeolian has as its predominating cadence chord G major (bVIImaj) or G7 (bVII7).
Many minor tunes substitute the V major or V7 to act as the dominant chord. But the moment you use a Vmaj or V7 chord in a minor tune, you are no longer in pure aeolian - you have now gone into the realm of harmonic minor or melodic minor (which is NOT the same thing as the aeolian natural minor).