I like the IFR-idea of staying in one scale as long as possible.
Right now I’m working on the Blues Mastery Course and find myself wondering why I should “think” a standard blues as 1D7, 4D7 and 5D7.
For me (at least right now…) it seams logical to think of a blues scale as derived from a Dorian Scale, which would make the chords 2D7, 5D7, 6D7.
Am I making a mistake?
Why should I consider the Blues root as 1?
I’m not familiar with the Blues Mastery material, so take anything I say with a pinch of salt!
Wouldn’t a Dorian scale give you a minor tonality. I know Blues is a strange beast, and doesn’t fit into our convential music theory modes. So, maybe you could use note 2 as the tonal centre, but it probably wont align with IFR documentation.
Major key Blues has that tricky flat third to the natural third of each chord. So the 1 4 5 that means b3 b6 7 respectively. Then the blue note is vital for each chord and that adds the b5 7 b2 respectively. So the only correct scale for the blues is the chromatic scale;
1 b2 2 b3 3 4 b5 5 b6 6 b7 7
Best of luck!
One if the strange & wonderful things about music is that there are very few actual ‘mistakes’.If it works for you, then it’s at least sort of ‘right’. 
However, there are many many variations on right - maybe nearly as many ways as there are musicians? LOL!
David Reed ( @ImproviseForReal ) is a very deep thinking & thoughtful guy. He will have designed the Blues Mastery course the way he did for reasons. He’s a very busy guy but if we’re lucky I hope he may have time to enlighten you himself?
Thank you for your answer! Yes, Blues seems to be a strange beast 
As far as I’ve understood so far, Blues means a “minor” scale (like minor pentatonic) played over a “major” chord progression.
Whenever I see a D Blues scale I think: Oh, D Dorian scale with #5 and without 3 and 7…
Thank you!
I really do like THIS Blues scale.
Perhaps I start thinking Blues that way - which would make it just ONE scale for everything - even für Jazz
Thank you for your answer!
Its just that after working with the IFR method for some years now, whenever I come across a Blues scale, I think: Oh, a Dorian scale with a #5 (and with no 3 and 7)…
Your answer kept me thinking.
If the key of the Blues is my 1 than it’s like you say.
If I think of Blues as derived from a dorian scale the blue notes are of course not b3, b5 and b7, but like this:
Thinking in the Blues root as 2 doesn’t change the character of the chords - it just changes how I think about them.
We are used to think Blues around b3, b5 b7. But would it work otherwise?
Am I making a mistake???
It works from a math point of view. I’ve tried playing a 12 bar using level 2 as the root and I could get used to it.
We are already in an odd position using IFR as opposed to changing the 1 note for every new chord like the rest of the world, so altering the flat note numbers away from b3, b5 and b7 might be a bridge too far.
Note also that we all refer to the one, four and five chords in blues, assuming the root of the tonal centre is 1. So in your example you would be in the key of C with a tonal centre of D. Normally, that would mean playing a Dm based melody (like Santana does a lot) but in your proposal you would be subverting level 2 to be a major sound. All chord charts using Nashville numbering will have the I chord as the tonal centre. I’d probably find it hard to transpose it as the 2D chord etc.
Personally, I find using the 1 as the root works fine for me as I am already familiar with where the flats occur in the blues scale, and the minor and major pentatonic scales (I am trying to avoid using boxes though and move my brain to using IFR numbers throughout the progression).
There comes a point where you don’t think about the numbers much and just play using intuition for deciding what the next note (or phrase) should be. I am getting there slowly 
.
For info: Blues is my main (retirement) interest, so I’m happy to discuss this topic all day. I bought the IFR Blues course when it first came out.
Thank you very much for your answer. I really appreciate your input.
Coming from a Folk background and having spent literally years in what IFR calls the second environment I might be biased. Blues is relatively new to me and so I might tend to lean towards what is familar.
Currently I’m thinking about why not be consistent with IFR? I AM thinking music differently already - so why not do it consistently? (Maybe because I would need an interpreter when speaking to other musicians… )
I just started early retirement and I’m hoping Improvisation and Blues will become my retirement interest