As a novice getting the hang of playing any instrument, especially a CBG is very confusing. Playing the instrument in a Blues style is even more complicated if you do not understand its development. I have yet to find a good primer on blues. I am not an expert but the following appears to be valid from all I have read:
The major "D" for blues has a "D" for the I chord, and "F" for the iii, a G for the IV, an "A" for the V, and a "C" for the vii. A minor D7 uses the notes of 1 = D, 5 = A, 3 = F, and 7 = C. The Major D7 uses D - A -F# or Gb - C. the big difference is the F and F#. Tuning was developed to facilitate easy playing of these 7th chords and the major and minor chords.
Contrary to popular belief the earliest known blues is from Appalachia. It is mostly settled by "Gaelic" people of Welsh, Irish, and Scottish descent, and blacks. The experts believe the Gaelic people [which included the Druids] migrated in the far ancient past from India, as did the Gypsies. So first look at other scales related to this heritage.
The Hindu scale is 1 • 2 • 3 • 4 • 5 • b6 • b7. The Ethiopian scale is 1 • 2 • b3 • 4 • 5 • b6 • b7. An Oriental scale is 1 • b2 • 3 • 4 • b5 • 6 • b7. The Spanish Gypsy is 1 • b2 • 3 • 4 • 5 • b6 • b7. Adding to this music style mixture were Italian and Portuguese people who used the Maximilian scale. And in this area were also Germanic and Italian neighbors.
As a result of all these cultures they gravitated toward a compromise scale called the Dorian. The Dorian scale is 1 • 2 • b3 • 4 • b5 • 5 • 6 • b7. Combine all these cultural scales and you have a good 7 note blues scale for riffs and arpeggios. 1 • 2 or b2 • 3 or b3 • 4 • 5 or b5 • 6 or b6 • b7. So, to round out the blues scale you can add elements of the other related scales. Over time the The abbreviated Pentatonic Blue scale of 1 • b3 • 4 • b5 • 5 • b7 was often used.
The African slaves brought to America and the Appalachia a unique "instrument" to teach children to play music. It is the forerunner of the Diddley Bow. On the side of the house a one string device was fixed and was played by "fretting" it with a piece of bone, ceramic, or metal. This "slide" fretting carried over into the Blues style. Tuning was often modified to facilitate the slide style.
A style of chording followed on multi-string instruments to facilitate this slide style and blues tunings. However, real blues is never slide alone but requires some finger fretting. The slide set up allowed for the bb often encountered in Blues.
In Blues the root can be played as a major, minor or 7th, This also holds true for the IV and V. The vi is always played as bvi, the vii as bvii, and the iii as biii. The I for "D" can be D, Dm, or D7, the IV G, Gm, or G7, the V as A, Am, or A7, the vi as Bb or Bbmaj7, the vii as C and the iii as F.
Finally, there is a lot of commonality in all the Appalachian music. Blues, blue eyed blues, bluegrass, and Bakersfield country all share a lot of the elements and instruments developed in the Appalachian area to accommodate these styles. To truly understand Blues requires some understanding of its Appalachian cousins and the Appalachian instruments it originated on.
Comments
The History Of The Blues: The Roots, The Music, The People by Francis Davis is a very interesting book...
It may not make any difference to some but for me learning about the origins of the music that has had such a profound influence on my life is important. Blues is about emotion more than scales or anything else. That doesn't mean you can't do the analysis too, or that doesn't help either, but I believe that connecting with the roots of the music and the people that played it in the early days is a big deal. Classical students learn about plainsong, Bach etc. for good reason. It puts the music into a cultural context and helps you to express it, both stylistically and emotionally.
Attempting to rewrite history like this does no one any favours. it bears no musicological or historical analysis, and would have the true pioneers of the blues laughing from their unmarked graves.
You know I keep hearing about how the early players of this that or any kind of music were illiterate, didn't know scales or chords or whatever and it's hogwash.
Folks chiming in after the fact are confusing musical literacy with communication.
If you don't think early blues/folk/country/bluegrass/etc musicians knew and used what we call scales and such you are not listening to the music.
The players may not have been able to read sheet music or know the proper musical terms but they sure as hell communicate the musical ideas of those concepts effectively.
A scale is a group of notes that sound pleasing together that have been given a label.
Anybody sitting down banging around on a vibrating string and varying the length is eventually going to come to the same conclusion. Now said person might not give the grouping the "proper" name but the sound will be the same and when shown in person to another individual the musical concept will be passed along, i.e. communicated.
I'm going to play Devil's advocate here, but playing blues is not not confusing or complicated, and on a 3 string guitar it's very easy.
You most certainly don't need to read anything about the development of this musical style to play it, you don't need any notes and numbers. Forget all those notes, hit the open strings and just use the 3rd fret, any string any order, don't bother with a chord change it's not needed.
Doing 1 chord and 3 chord songs is simple - I've taught over 1000 people of all ages to play and it usually takes about 10 minutes maximum for people to get the hang of it. Just get a rhythmic groove going...that's the main thing.
After reading this I would suggest that further research and critical analysis is necessary.
African polyrythms gave rise to the crucial shuffle and highly syncopated patterns that characterise blues, and from there all contemporary music. You won't find anything like them in the Appalachian tradition.
The minor pentatonic scale was common in West Africa as well as other places and given other African influences such the strong rhythmic elements, structural factors like call and response, it's development in African descendant communities I'd still say that any Appalachian influences are relatively minor.