Asle

The notes of the major scale are listed in order. For instance take the C Major scale (which has no sharps).
the notes are C,D,E,F,G,A,B. If you now number them in that same order C being one D two etc those are considered the scale degrees. A major chord is constructed from the 1,3 ad 5 of the major scale. Thus if you know the notes of the scale you can discover the notes to construct the chord. It sounds complicated but is in fact simple. And exactly the same goes for a chord progression so a 1,4,5 is a progression of the Chords from the relevant scale. Thus the 1,4,5, of C is composed of the C, F and G chords.

The Scale of A has 3 sharpened notes marked with # in notation. The A scale looks like this A, B, C#, D, E, F#, G#. You can immediately count up and see the 1, 4, 5 of that scale are respectively the notes A,D,and E. Thus the 1,4,5 progression of A is composed of the A D and E Chords.

Using the A as an example it is easy to work out the Chords for any blues progression if you either know the notes of its relevant major scale or simply by a pattern method.

If you take the key of A major starting at the 5th fret of the sixth or bass string you have an A note move to the 7th fret and you have a B that is the 1 and 2 of the scale now move to the fifth string and you get a D note at the 5th fret right under the 1 or A well that is the 4th of the note of the scale so the note of the major scale that is the 3rd is right before that at the 4 fret and is a C# (3rd) at the 7th fret of the fifth string you have an E which is the 5th of the A scale. So if you just now look at those you will see that the A is above the D and the E is two frets up from the D it forms an ‘L’ shape well if you take that shape and move it up to the 8 fret on the sixth string you would have found a C note and its 4 and 5 below accordingly on the fifth string at frets 8 and 10.

We stopped on the Fith string in the A example at the 7 fret of the 5th string. Well if we add three more notes from the fourth string starting with the F# note at the 4th fret of the 4 string and then move up to the 6th fret where we get a G# and move up one more Fret and its another A note which is an octave above the A you started at on the sixth string so if you run through those notes you will hear the major scale which should immediately sound familiar to you.
There is quite a bit packed in there to get to grips with but it is easy if you just take a look and time to run through and see what I have talked about, then you will have it.

I hope that helps.

JohnStrat

An additional pattern can be found for the 1,4,5 by reversing the L shape. As mentioned above the A 145 progression forms an L shaped pattern starting with the 1 degree an A note on the 6th string at the 5 fret, the 4th immediately below on the fifth String at the Fifth fret for a D note and then again on the fifth string at Fret 7 you find the fifth of the progression an E note.

Well if you make a reversal of that L shape (where the E note of the 7 fret fifth string is swapped for a G at the 3rd fret of the sixth string) You now have the notes D,A and G highlighted by the pattern.
Those notes compose the 145 of the D major scale D,E,F#,G,A,B C#. You can now see the D is the 1, the A, is the 5th and the G is the fourth.

You should also get your head around the intervals.

The intervals are the spacing between the notes necessary to create a particular scale. W W H W W W H is the formula which I remember by thinking 2131. The W stands for a Whole step and the H stands for a Half step. my 2131 therefore = 2 * Whole, 1 * Half, 3 * Whole, 1 * Half.
These represent the steps of the major scale or intervals of it. A whole step on a guitar is two frets distance and thus a half step is one fret distance apart.

So using the formula 2131 if we take the E string and say we want to find the E scale major notes it is simply a matter of starting by playing the open string and using the stepping formula. The Open E is the starting point and is the first degree. Then next you need to know the right interval to find the next note up the E scale so using the formula you move a Whole step to find the F# at the second fret, next you move another Whole step and thus 2+2 takes you to the 4th fret which is the G#. The next step is a Half so that gets to the fifth fret which is an A note. You then move up using Whole steps ie 2 fret intervals to discover the next 3 notes of the scale and finally a half step. The notes found in that order are 7th fret a B note, at the 9th fret a C#, the 11 fret a D# and then at the 12th fret you have moved up to another E. From here the whole process now repeats being one octave up from the start base E. So now you have the means of working out the notes of any major scale and the the means to find any major triad(three note) chord.

I hope I have not made any mistakes in what I have written and that it is a help for you.
JohnStrat

Simplest way I can tell you to think about it is go sing or play a simple major scale (think Do, Re, Mi, Fa, Sol, La, Ti; like the song from “The Sound of Music” movie, “Do-Re-Mi”.

Instead of giving the notes names like C-D-E-F-G-A-B, or Do-Re-Mi etc, give each a number starting with 1.

Then in any key, and from any starting note, you can figure out the 1st chord or note, the 4th chord or note , and the 5th chord or note.

So in the key of “C” the 1,4,5 would be C,F,G. – Hope that helps a bit. –
1-2-3-4-5-6-7
C-D-E-F-G-A-B

in key of C, 1 is the root note of C scale: C
in key of C, 4 is the 4th note of C scale: F
in key of C, 5 is the 5th note of C scale: G

1-4-5 chords in key of C: C-F-G
1-4-5 chords in key of D: D-G-A
1-4-5 chords in key of E: E-A-B
etc.