'The Blues' Modal Theory

A new philosophy to consider...

First of all, the album cover.  Why not enjoy some OP blues while reading this article to keep you in the mood?

I made a video introducing the concept that, using the notes of the blues scale over any chord type which is based on the notes of the blues scale it comes from, works... sometimes better than others but it works and is a nice simple way to acquire six notes (the blues) for improvisation, knowing that they don't all sound 'bluesy' - hence the title of my video:  Unbluesing the blues scale.

Before you watch the following video, (let OP finish!), understand the following:  whatever chord you're playing, whether major or minor-triad based or dominant or major 7th inclusive, the blues scales in which the root of that chord exists, will work and provide varying results.  Blues is about dissonance, so it's ok, as long as there is musical context and not doing it in isolation, that some note choices go against 'traditional music theory'.

On the assumption that you have played around with this idea and perhaps identified your favourite note values and chord types, I'm going to present you with the official Blues Modal Theory law, using diatonic and non-diatonic, preferential chord types.  Understand that a mode is just another way of saying 'scale inversion', just like how one can invert a chord: same notes, different starting point.  The blues scale has six notes thus a root position and five others.  I will demonstrate in the key of Bb, just to make you use your brains a bit more than Mr. C 'All the White Notes' Major.  What you will learn is a template so it instantly applies to every key.

Bb major:  Bb, C, D, Eb, F, G, A... Bb.
Blues template:  1, b3, 4, b5, 5, dom7.
Bb blues:  Bb, Db, Eb, E (I say E not Fb since F also exists - don't nitpick), F, Ab...

The names of the modes in traditional modal theory are, in order 1-7:  ionian, dorian, phrygian, lydian, mixolydian, aeolian, locrian... so it seems logical to use these but stick 'Blues' to them.  I quickly realised, however, that the flat third could be confusing to say 'minor Phrygian' or 'flat five Mixolydian' so, for now, until I become a Greek God, let's simply refer to them as:  Blues 1, Blues 2, 3, 4, 5 and 6.  This refers to the 6 degrees of the blues scale.  Therefore, playing Blues 4 Mode would mean, in Bb, to play the notes of Bb blues from the fourth note of the scale, E, giving 'E Blues 4 Mode':  E, F, Ab, Bb, Db, Eb.  Noice.

Now comes the diatonic bit.  Diatonic chords comes from playing the 1 3 5 7 of the major scale of the key of the chord you're playing (the notes of Bb blues in this case) and lowering or raising, (usually lowering) by a semitone the note or notes which are not in the master scale (Bb blues in this case).  Let's see what chord types we get:

Bb, D, F, A.  Which notes are not in Bb blues?  The D and A.  We lower them a semitone and now name the resulting chord:  m7.  Therefore, we have Bbm7 but since the blues uses both a major and minor third, plus a perfect and flat fifth, we have multiple choices to consider.  Therefore, we can add 'a, b, c...' as necessary to the mode label... thus:  Blues Mode 1a = Bbm7 (Bb, Db, F, Ab) / Blues Mode 1b (using major third) = Bb7 (Bb, D, F, Ab) / Blues Mode 1c (using minor third and flat five) = Bb half diminsished or Bbm7b5 (Bb, Db, E, Ab) / Blues Mode 1d (using major third and flat five) = Bb7(b5) (Bb, D, E, Ab) - this is last because it's least common.

Next:  Db:  Db, F, Ab, C.  Which notes are not in the Bb blues?  C.  We can't lower it to Cb/B because that isn't in the blues either, but C#/Db is, so we simply get a major triad here but you could, if you wanted, make it a 6th chord, this would be the second option, so Blues Mode 2a = Db Major triad (Db, F, Ab, Db) / Blues Mode 2b = Db, F, Ab, Bb (which works).

Next: Eb.  Eb, G, Bb, D.  Here, the G and D are not available so can we lower G to Gb?  No.  Raise it to G#/Ab?  Yes, so that's a sus4 (third up a semitone).  The D can be lowered to Db so that's dominant 7th:  Eb7sus!  Eb, G#/Ab, Bb, Db.  That's all.

Next:  E.  E, G#, B, D#.  E is fine.  G#/Ab is fine.  B is not.  D#/Eb is.  So E with a Bb is E(b5) but the D# is major seven:  EM7(b5) - but you would probably consider this a #11 for jazz theory purposes.

Next:  F.  F, A, C, E.  Lots here to change!  A becomes minor, C must be raised not lowered (#5, augmented), E can stay or be lowered.  The problem here is that you can't raise a fifth with a minor so let's raise the A, third, to make it sus4M7:  F, A#/Bb, C#, E or Eb so two choices:  Blues Mode 5a, the preferred, would be with Eb, the dominant 7th, since that works with the sus4 AND the augmented (#5).  Blues Mode 5b with the E, major 7, is not nice, nor is it a common chord type... but it can exist:  FM7sus4/aug.  So, make a note that Blues Mode 5 is the least attractive.

Next:  Ab.  Ab, C, Eb, G.  We must change C and G.  C can be raised to give sus4 in Ab.  G raised becomes Ab anyway.  Blues Mode 6 = sus4.

What you should now do is note the note values each mode gives.  For example, playing Blues Mode 2, the Db, the blues scale of Bb from Db to Db gives what note values in Db?  Root, 2nd/9th, minor/#9, major third, fifth, 6th/13th.  Nice note values!

So whenever you see these chord types, know which Blues Mode it is and play the notes of the blues scale of whichever one the root note of the chord is currently in that position.  For example, if you see G7sus4, know it can be the 6th Blues Mode, and G is the 6th note (dominant 7th) of A, so A blues will work over G7sus4, as if we did this process on the A blues scale.

Just to summarise, the Diatonic Blues Modes are:

1.  m7 (a), 7 (b), m7b5 (c), 7(b5) (d)
2.  major triad (a), 6 (b)
3. 7sus4
4. M7(#11)
5. 7sus4+(augmented) (a), M7sus4+ (augmented) (b)
6. sus4

Have fun!  Related video coming very soon to demo this article.