I am very new to even the basic concepts of music theory so there might be something inherently wrong in my question but here it is,
There are some common chords progressions which are denoted by the Roman numerals , for e.g. I IV V , which for C Major scale is C Major,F Major and V Major
What I understand from this notation is that for a particular scale, a chord progression whose root notes are based on the 1st , 4th and 5th notes of the scale would sound good together. But my question is that it could be a minor or a major scale depending on the intervals between the root note, the 3rd note from the root and the 5th note from the root, but it seems to me that it is presumed that the chords would be major always. Why is it so?
The chords would be major in the case of a major scale because there the interval difference is in that manner. But they could easily be a minor chords or mix of both for a particular scale.
Another pattern that points this out is the
I–V–vi–IV pattern in which it is implied (as far as I understand ) that the chord based on the 6th note of the scale would be a minor one. But this can't be said universally for all scales , the intervals won't always in this manner.
Is there smoother meaning to using upper and lower case numerals ?