Why is Chord Theory so much more complex in Jazz than in Classical Music?

Question

What is your response to this quote fro Wikipedia:

"One important feature of jazz is what theorists call "the principles of chord-scale compatibility": the idea that a sequence of chords will generate a sequence of compatible scales. In classical major-mode harmony, chords typically belong to the same scale. (For example, a I-ii-V-I progression in C major will typically use only the notes of the C diatonic collection.) In jazz, a four-chord progression may use four different scales, often as the result of chordal alterations. For instance, in C major, a jazz musician may alter the V chord G-B-D-F with a flattened fifth, producing G-B-D♭-F. An improviser might then choose a scale containing these four notes, such as G whole tone (G-A-B-C♯-D♯-F), G octatonic [or symmetric diminished] (G-A♭-B♭-B-C♯-D-E-F), or a mode of either D or A♭ melodic minor ascending (G-A-B-C♯-D-E-F or G-A♭-B♭-C♭-D♭-E♭-F respectively). In each case the scale contains the chord tones G-B-D♭-F and is said to be compatible with it. This notion of "chord scale compatibility" marks a fundamental difference between jazz harmony and traditional classical practice."

Source:
http://en.wikipedia.org/wiki/Jazz_scales

Answer 1

It's very self explanatory, just read it again.

Answer 2

basics are similar, but there are definitely some differences. some things are spelled differently and there are different terms for the same kind of chord. like... what jazzers would call a tritone substitution, classical would spell with a different enharmonics and call an augmented 6 chord... or.. something like that... and different symbols are used, like classical doesn't use that triangle for major. but even at different schools the same style isn't always exactly the same. like "real book jazz notation" vs "berklee jazz notation" is a little different and even in classical some people don't like "I 64" and instead say "V 64" to show that its really a V with a suspension instead of a tonic harmony. but if you study jazz and then classical or classical and then jazz, you will recognize a lot of the same concepts. it wont be like starting from scratch.

Answer 3

The scale used is chosen because it is in harmony with the chord used -- and in that case it's just a matter of terminology -- classical rules of counterpoint and voice leading are in agreement with jazz theory. Neither is more or less complex than the other.



Consider this -- if we are using the minor mode, a V7 chord requires the use of the "harmonic" minor form, while a iv chord would require the natural minor form ("descending" melodic -- a misnomer, but there it is). This is in perfect agreement with jazz scale theory.



If the chords are altered, (like the use of the flatted fifth in a V7 chord) then the scale must agree and flat the same note -- or we're going to get some not-so-great sounding counterpoint.



The last sentence of your quote is essentially incorrect. Scales must agree with harmony, even in traditional classical practice.



Cheers,

G.