Agree with all of what you say Mac. In fact of all the posts about chords and scales we've had on this forum I can't think of a more important one than yours here. it's absolutely fundamental to get these sounds in your head as most players think in these smaller groupings when building improvised lines. (remembering of course the inversions of all the above)

I see where you're coming from with your ballistics analogy..its possible to over-analyse here and fail to let your ear do the judging.
However think it's a good idea initially to categorize these tetrachords in order of dissonance or at least as examples of diatonic major/minor, chromatic and atonal tetrachords. It gives you a basis for organizing and selecting the material, controlling the tension and release of your lines as well as aiding the learning process by breaking it down into even smaller components. (btw I'm also thinking of the tetrachord as being a 4 note grouping up to and including the b5th not just the perfect 4th as defined traditionally. )

The entire system of major minor melodic minor, harmonic minor and harmonic major along with whole tone and diminished scales can be built from combinations of the following 8 simple formulas.


DIATONIC semitones
Lydian 2,2,2
Ionian 2,2,1
Dorian 2,1,2
Phrygian 1,2,2


CHROMATIC semitones
Hungarian Major 3,1,2
Hungarian minor 2,1,3
Harmonic 1,3,1
Spanish 1,2,1



Beyond that you've also got the atonal tetrachords most of which have two semitones.(the Harmonic and Spanish listed above are in both categories)
They're good to know for compiling exotic scales and all the other 1 octave symmetric scales possibilities. so you should make an inventory of those too.

CHROMATIC/ATONAL
1,1,1
1,1,2
1,1,3
1,1,4
1,1,5
1,2,1
1,2,3
1,3,1
1,4,1
2,1,1
3,1,1
4,1,1



As far as scales are concerned it would be a good project to harmonize any of the main tonal scales and their modes using BIAB and try superimposing these modes and their chord voicings on a section of a well known tune. You dont see BIAB used that way very often and it would be a nice change from standard II V I arrangements.

Regards


Alan

Last edited by alan S.; 01/31/10 04:49 PM.