21. Blues scale

In the previous episode:
"All this to say 2 things:
- pentatonic scales are awesome, they are easy to use and can be used in many ways and are present in a lot different cultures
- Some musical concept from other cultures are not always compatible with our occidental music theory, even though some cultures have adopted some of our western concepts.

But sometimes, it is our music theory that evolves to implement something new."

The example I'd like to take for that is the blues scale.

BEATS & BOBS

Here is the blues minor scale of A, it's made of:
A - C - D - Eb - E - G
Apart form the fact that this sounds awesome, It is just like the minor pentatonic scale, but with this diminished fifth added. This added note is a note we call "blue note", but where does it come from ?

it makes more sense to look at the major blues scale to find that out. The relative major of A minor is C major, so the C major blues scales would use the same note, but starting from C. Thats:
C - D - Eb - E - G - A

Seen like this, the blues scale is like a pentatonic major scale, with a minor third added. So it has both a minor and a major 3rd. And this is exactly how this extra note was introduced in the scale, as a minor 3rd.

See you can use a major pentatonic over a major tonality of the same name. Like a C major pentatonic over a song written in C major. All notes or in common so it will work.

You can use a minor pentatonic over a minor tonality of the same name, like the C minor pentatonic over a song written in C minor. All the notes are in common so it will also work.

But you could also use some elements of a minor pentatonic over the major tonality of the same name. Like using some notes of the C minor pentatonic over a Song in C major. It is not as intuitive but that's what a lot of early bluesman did. Because when a major chord is playing and you play its minor 3rd over it, it creates a friction between the minor 3rd and the major 3rd that are then coexisting, and then this minor 3rd wants to go up to the major third of the chord to be resolved.

So you can use this Eb as a bridge to go to a E, or use this Bb to go to a B. These notes that are specific to the minor scale, are better used as transitions to go toward a note that is part of the major scale that is used for the song. If you finish a melodic line on a note that is not in the major scale, It will not be as effective as you would then finish on a dissonance that is not resolved. But using these dissonances as transitions has this particular blues colour to it, which is very nice.

Another way to use this dissonance between the minor 3rd and the Major 3rd of a chord is by using a dominant 7#9 type of chord. This is a regular dominant 7 chord, made of a root note, a major 3rd, a perfect fifth and a minor 7th, to which we add an augmented 9th. 
Just like a regular dominant 7th chord, this type of chord is often used on the Vth degree of a scale. So if we are in C major, it could be seen on the Vth degree G.
And our G dominant 7 #9 chord would be made of the root note G, its major 3rd B, its perfect 5th D, its minor 7th F. And the 9th should be A, but we need a #9, so we raise it by a semi tone which gives us a Bb.
As you can see, we have then in this chord a Major 3rd B and a Bb which is equal to a minor 3rd.
This chord is dissonant, but works because these two 3rds are spread  out on two separate octave.
Because it is used on a Vth degree, this G7#9 chord should resolve well to a C chord, which is our Ist degree. So we have a nice V to I authentic cadence.

This dominant 7#9 chord is also called the Jimmy Hendrix chord because it is a chord he loved and that he helped popularize notably with his song Purple Haze.

The chord progression cycles between the chords E7#9, G and A.
Here's the E7#9 which can be considered as the degree V, with the notes E, G#, B, D, F## which is a G natural
Then the G chord, which uses notes already in the E7#9, the G, the B and the D
and then the A chord which is the Ist degree, that resolves well after the E7#9

So when you play over a major tonality, you can use a major pentatonic, but you can also use notes from the minor pentatonic.

So if you mix the major pentatonic and the minor pentatonic together, to make it only one scale, for a tonality of C for example, 

This would make this scale:
C - D - Eb - E - F - G - A - Bb

You can use this scale as is, but is could be tricky to use sometimes as the risk of friction would necessarily increase. 

So the blues scale is a simplified version of this, where we take the major pentatonic, and add only the 3rd of the minor pentatonic. This makes it easier to use because then we only have to be careful of this one note. And we still have access to this blues flavour, given by this little chromatic bit, introduced with the introduction of this minor 3rd.

This gives us the major blues scale. Here the C major blues scale for the example.

And if we take the relative minor of this scale, which would be the scale using the same notes, but starting from A, we have now the minor blues scale.

This is how we end up with a blues scale that looks like a minor pentatonic but with a diminished fifth added. This Eb that have been added is 3 tones above the root note, which is an interval of a diminished fifth

This is something that is the result of ages of evolution, and the precise origin of the scale is unclear, but it is the result of repetitive use of unorthodox methods that created this scale, that is one of the most used in rock, blues or jazz. It is one of the first one a beginner guitarist would learn for improvisation. Because it works on anything.

And the morality I'd like to take out of that is that if music is a language, there's always a way we can communicate, even though we use it in different ways or in unorthodox ways. And we are able to make up our own slang and dialects, that maybe someday will find their way into the dictionary. 

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Take care, and I'll see you next time.

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