If the theory of blues as just intonation intervals is true, then blues musicians are bending their notes to make them more in tune. Certainly my experience of playing the music is not that I am intentionally playing dissonances, it’s more like an alternative system of consonances.
The best source on African precursors to the blues that I know of is the book Africa and the Blues by Gerhard Kubik. I summarize some of it here: The blues and the harmonic series – The Ethan Hein Blog
Hey Rory,
Im certainly not implying any one person thinks a certain way. Just a general theme that usually arises when the theory v playing topic arises.
Certainly when doing improv etc, there’s obviously no place for any theoretical musings. Its more of an organic thing I think where theoretical frameworks, concepts etc, over time, eventually seep into the subconsious in a practical way, and come out in your playing; spouting ideas that perhaps would not have happened otherwise.
Cheers, Shane
If anyone wants to continue learning whats in the Paul Davids video Rodger posted Justin has a series of lesson on these concepts.
Appreciate all the input from the various viewpoints. With a topic like this, there’s been the inevitable subtopics that have evolved etc, which is all great, and pretty much expected with a broad topic like this. Can only be of help to all of us.
I suppose the main gist of my post was to bring to the discussion table, that, by acknowledging and exploring the ‘parent’ keys of these 3 dominant 7 chords, it appears to open up alot of opportunities for endless diatonic harmonies within the Blues, while at the same time potentially enabling one to see them at work, particularly in more modern blues.
All very fascinating, and years of learning and experimentation ahead…
Cheers, Shane
So to take this a step further with my limited theory knowledge, if you play a G major pentatonic over the A you are almost playing the A minor pentatonic plus the 9th. The G is also the flat 7 of A. Playing the D major pentatonic over A adds the 9th again and the 6th. All harmonically correct. Someone will tell me shortly this is a mode…
If playing a solo which switches between major and minor those are all available note choices.
Expand G major pentatonic to incorporate all the notes of the G major scale, switch the focus entirely so that A is the root note - you have A Dorian. A minor pentatonic plus 6th and 9th.
Similarly with the full D major scale. Make A the root and you have A Mixolydian.
Welcome aboard 
Kudos for writing the article as well as jumping in the conversation here.
I only skim-read it and followed the first bit on harmonics before glazing over but may well come back for a more thorough read.
I like the way it sounds ‘logical’ 
Thanks. Thinking about it, all the notes in G major and D major are present in either the A major or A minor pentatonics.
This, I guess, is why all those dominant 7s work out and the blues is a mixed brew between major and minor.
Thanks for starting the discussion. Any discussion like this brings some understanding and more importantly ideas to try out in practice. As you said if practiced enough these things should appear in playing without thought. It is a long way. Might never happen for me with the amount of practice time I have available, but every day a little closer. I will quote here (if permitted) Tomo Fujita: when practicing think everything, notes, intervals, scale degrees, tone, dynamics, muting. When playing, just play. Years ago when I started learning (luckily with Justin) i wanted to play songs and solos. Last couple of years I want to play the guitar, if you get what I mean. Playing songs is difficult. Playing guitar even more.
Thanks so much Shane @sclay and also @Richard_close2u Thanks to you and this topic I have finally got to grips with modes and now understand how they fit musically.
Don’t think I’ll be playing any of those pesky semitones soon though; firmly stuck with pentatonics. Peter