Guitar Slim wrote:... where I really get confused is applying modes to a complex set of real changes -- one in which the notes of the chords don't necessarily all come from the basic key, and where the tonal center is often difficult to determine. What principles apply? How do you determine what mode to use over what chords in the progression? And even in this example, I have to wonder if understanding the chords and their relationships to each other is more important than thinking in terms of modes.
Inquiring minds and all that...
Personally I have come to think that the semantic issues arising from the word "mode" have become truly hilarious.
The permutations of possible relationships between "key" and "mode" are many, because neither is properly defined, and so the question of what "mode" "belongs" to what "key" generates a lot of confused crosstalk such as you have read on the last 20 posts. Does "A Phyrgian" "belong" to the "Key of A" or to the "Key of F" and so on. Ok, whatever. And we get accusations of "No, you're wrong! Yes, I'm right!" flung around.
I'd like to offer a simple bypass for the confused (while the cognoscenti continue their arcane discussion!)
This idea comes from the guitarist Steven King (no, not the novelist.) King's workable suggestion, which has served me well, is that it is un-necessary for most practical purposes to know the "modes". Instead, learn exactly two types of scale: major and harmonic minor, in all keys. Then practice being able to start them on any of the six other notes of the scale besides the root. This gives you, for any key signature area in the circle of fifths, 14 possible octave scales, without any mental baggage other than "major and minor".
A knowledge of the circle of fifths, and the chord families derived from each major and minor scale is of value at this point.
A chord family consists of those chords which can be constructed from a given scale with no alterations, except for the characteristic shifts of the 6th and 7th degrees of the minor scale.
See this chart:
http://www.guitar-vacation-retreats.com ... le5_01.jpg
and this page:
http://www.guitar-vacation-retreats.com ... ifths.html
For instance, the chord family of C Major: Cmaj7, Dm7, Em7, Fmaj7, G7(dom), Am7, Bm7(b5) [aka B-half-diminished.]
The A Minor chord family includes the C Major family plus commonly E7 and G#-diminished-7th, plus possible variants of all the other family members where F or G may be sharped (i.e., uncommon chords like C-aug-maj7, etc, plus D7, F#m7(b5), etc.
From this knowledge, it becomes possible to recognize groups of chords from given families, which therefore indicate the scale required. For basic practice in chord families, study the two tunes (1) "Manha de Carnival" by Luis Bonfa, and (2) "Autumn Leaves" by Joseph Cosma (1905-69) (not Johnny Mercer, who only wrote the English words.) These two tunes require switching back and forth between the major scale and its relative harmonic minor scale, i.e, C major and A minor (with two instances of D minor) in "M de Carnaval", and between G major and E minor in "Autumn Leaves" (disregarding the difficult chromatic series toward the end where a descending chromatic scale actually works fine and suits the mood).
When the chords come from areas all over the circle of fifths, it is necessary to look for groups of two or more chords that indicate a given chord family, and make a choice of scale if the chord group may belong to more than one family. In the case of a notoriously difficult tune like Coltrane's "Giant Steps", you will be no more challenged than many other musicians.
A "ii-V" progression defines a scale by itself. There are 24 possible common "ii-V" progressions, one for each major and harmonic minor scale, and it is of value to learn them.
Some chords require hybrid scales. Knowing the "modes" will not help you with those, anyway! since the "modes" by definition are inversions of the major scale. Discussion of those hybrid scales would make this post too long, which it is already.
In the case of "modal" jazz tunes requiring a particular mode, you will discover that one of your scales from the above set of 24 WILL fill the bill for almost all cases. A little experimentation will discover which one is appropriate. For instance, for Chick Corea's "La Fiesta", which specifies "Solos in Spanish Phyrgian", mixing your C Major and A Harmonic minor scales will work out fine, but using "E" as the de facto tonal center, which you easily can do because you have practiced starting these scales on any note.