Huh, a long post ahead as, at least I think so...
I'm wondering about one thing. I have a C major scale (for example). Now, I know all the notes there are in that scale, and I know that rule that major chords are on I, IV, V, and minor ones are on ii, iii, vi. Last one is diminished. Right?
Well, let's take a look at the major scale formula:
Let's say I want to improvise in the key of C, let's say I'll play C-Am-G (just invented the progession).
I can find the C note on the fat E string (8th fret), and then I can build a simple triad by using notes on D, G, B -> 1-3-5.
That's a C major triad, right?
After that, I go to the 5th fret - A note. Here I can do the same thing except I have to flat the note on the G string. I got an Am chord, if I'm right.
Then I can repeat the procedure for the G one, too. I build a nice G major triad.
I was wondering if this is a good approach, because I'd like to do chords, and this seems to make sense to me. After reading Kirk's lessons, I came to a conclusion that everything comes from a major scale, with some changes. I see this as one of the ways. Please tell me if this is correct. Thank you

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