Topic: Scale Structure and Blues Chord Progressions

[Johnm]

Hi all,
The proliferation of threads talking about Blues forms and chord progressions of various types, listing the progressions in the numerical abstract (I, IV, V, etc.) made me think it might be helpful to post a little explanation of scale structure and how it pertains to chord progressions.

The major scale has eight notes with the first and eighth the same.? They can be named either do-re-mi-fa-sol-la-ti-do, or simply given numerical designations, I-II-III-IV-V-VI-VII-VIII.? The scale conforms to the following system of steps:
?1 step? ? 1 step? ? 1/2 step? ? ?1 step? ? ?1 step? ? ?1 step? ? ? ?1/2 step? ? ? ?
I--------II--------III----------IV---------V--------VI---------VII----------VIII
The letter names of the notes that comprise the scale always occur in the order: ABCDEFG, though you may start on any letter, and in any given scale, the only letter that appears twice is the letter that begins and ends the scale.? There are natural whole-steps between each of the lettered notes with the exception of E-F, which is a half-step, and B-C, which is a half-step.? For the lettered notes that are a whole step apart, like G and A, for example, there is a note halfway in between (the black keys on the piano), that, depending on its function, would be named either G sharp or A flat.? You raise a note one-half step by sharping it (#) and lower a note one-half step by flatting it (the flat sign looks like a lower case b with the circular portion pointed).? Using this information, you can construct a major scale off of any note simply by applying the step-wise formula:? whole, whole, half, whole, whole, whole, half.
Thus, a C major scale works out as:? C-D-E-F-G-A-B-C.? Since the natural half-steps between E and F and B and C coincide with where the half-steps must fall in the major scale, the C Major scale ends up having no sharps or flats.
What about other common keys used in country blues guitar, like E, A, G, D, or (less often) F?? You can figure out these scales simply by applying the step-wise formula. E major, for example, would work out as:
? 1 step? ? 1 step? ? ? 1/2 step? ?1 step? ?1 step? ? 1 step? ? ?1/2 step
E-------F#--------G#----------A--------B-------C#-------D#----------E
A couple of thoughts on this scale:
? ?* Since there is a natural half-step between E and F, it was necessary to raise the second note of the scale up to F# to get the whole step between I and II.? Note that the note is spelled F# rather than G flat because in a scale an E note of whatever type must be followed by an F note, of whatever type.
? ?* Since the II note was raised to F#, it was also necessary to raise the III note to G# to get the whole step required by the scale formula.
? ?* The half-step between G# and A falls just where it should in the scale, as does the whole step between A and B.
? ?* To get the required whole step between V and VI, it was necessary to raise the C note one half-step to C#, since there is a natural half-step between B and C.
? ?* To get the required whole step between VI and VII, it was necessary to raise the VII note a half-step to D#.? Once you have D# as the VII note, you wind up with the half-step up to the VII note, E, that the scalar formula requires.
If you are interested in knowing this information, construct the major scales in the flat keys, F, B flat, E flat, A flat, D flat, and G flat, and the sharp keys, G, D, A, E (you already have it), B, and F#.?
Once you know what the different major scales are, and the notes that comprise them, it is easy to describe chord progressions in numerical terms a la I, IV, V, etc., naming each chord by the note of the scale where it is rooted.? The advantage of thinking of progressions in the numerical abstract rather than in a particular key is that it enables you to transpose quickly to another key, should you be asked to play a song in a key other than where you learned it or played it before.? Another advantage of abstracting progressions numerically is that it enables you to recognize the same progression in different keys as really being the same thing, like C-A7-D7-G7, G-E7-A7-D7, I-VI7-II7-V7.
I hope this information helps those who are interested.? One of the great things about developing a degree of conversancy with this music theory-related stuff is that it equips you to participate in group music-making situations so much more easily than if you are in the dark about these matters.
All best,
Johnm

[Norfolk Slim]

Thank you John- that was an exceptionally helpful post.

I'm sure that many Weenies are well versed in theory - but my knowledge of music theory has just doubled!

It is very easy to play guitar with tab, and to learn blues progressions and the basic concept of I/IV/V in the most common keys without having any real concept of 'why'.? I have rather bumbled along, picking up only what was essential to what I was doing, or what was very obvious- and suddenly it all makes a lot more sense.

It wasn't too long ago that I was explaining to my wife, that I was often thrown by the apparent absence of an E sharp or F flat? ?? ?

Now I get it!

[Johnm]

I'm glad you found the post helpful, Simon.  Sometimes I wonder if I'm leaning on the theory a little too hard, but it really does help in an overall understanding of music, and if you constantly reference the theory back to what you hear when you play or listen to music then you begin to develop a really thoroughgoing orientation to what is going on with music.  Eventually it gets to the point at which simply looking at a progression mapped out in numerical chord symbols conjures up the sound of the progression being described.  If anybody would like an opportunity to try this out, take some of the major scales that you've constructed and go to the threads discussing 8-bar blues, 16-bar blues, or Circle-of-Fifth Blues, and work through some of the posted progressions in different keys.  Playing a common progression in a key other than where you've played it in the past may give you ideas for a new arrangement.
All best,
Johnm

[Prof Scratchy]

A helpful post indeed! It won't sink in immediately, and I'll need to practice counting out those steps and half steps - but it does provide a helpful formula. Practice will no doubt make perfect. And old dogs will learn new tricks!

[waxwing]

Since we know you have a piany handy, Scratch. As John M alluded, the C scale on all white keys is a great visualization.
All for now.
John C.

[Johnm]

Hi all,
It occurred to me that you run into some funny anomalies in structuring the scales that are farthest around the circle of fifths, G flat major and F sharp major, because of where the natural half-steps fall.? If we structure the G flat major scale, we wind up with the following:
? ? ? ?1 step? ? ? ?1 step? ? ? ?1/2 step? ? ?1 step? ? ? ?1 step? ? ? 1 step?1/2 step
Gflat------Aflat-------Bflat--------Cflat------Dflat-------Eflat------F--------Gflat
The funny note in this scale is the IV note, C flat.? We know that there is a natural half-step between the B and C and E and F notes.? By the time we arrive at the III note of the G flat scale, we have come to B flat.? Now we know that there is a half-step between the III and IV notes of the major scale.? Normally we would say that the note a half-step above B flat would be B, but because we already have a B note of some stripe in the scale, the next note must be a C note of some stripe.? Thus we end up designating the note we would normally name B, C flat, because the IV note must be a half-step above the III note and must have a different letter name.? Try figuring out an F sharp major scale and see where you run into a similar problem in terms of naming a note differently than you normally would, based on the scalar context.? Not that you will necessarily be playing a tune in G flat or F sharp in the near future, though you never know.?
All best,
Johnm?

[Johnm]

Hi all,
I'm just posting here since there have been music structure/chord theory questions recently and the first post here lays out a lot of basic information.  And the thread can keep going, too, to get into related areas that have not yet been discussed.
All best,
Johnm