I don't still understand the double notes construction...
For C shape, we built it according to the shape (or the arpegios changing the cord at reach step) 23 / 32 / 24 / 45 / 55 /52
So for A shape I though that will be 57 / 77 / 77/ 75 / 55 but instead Papa gates show us a different double stop: 77 / 55 /77 /54/ 77/45 / 55 / 45
What is the logic behind double stop construction? can we associative two notes of the scale ? because some association seems non conclusive (7 on A string and 4 on D string so E and F#) Is it because I associate the second and the third together ?
A double stop is two notes played together, which notes you okay together is usually determined by which intervals you like the sound of when played together. I mean you're probably not gonna do a double stop with a b5 and the root or b2 and the root.
E and F# have a whole range of reasons it can work. Sorry if this is a little bit too in deep as far as theory is concerned but basically those two notes are the 2nd and 3rd of D, 5th and 6th of A, b7th and root of F#, 5th and 4th of B, root and 2nd of E, 6th and 7th of G. In the end it depends on the sound you want to go for but you can really trace it all back to the chords and the fingering you play them in can be traced back to CAGED