The last couple of posts dealt with scales, chords, the Roman numeral system and how certain chords relate to certain scales. If you are using the C Major scale and you are deriving the chords that correspond to each tone of the scale, you would get, Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, Bm7b5. My question is how come the I, IV, V progression refers to all dominant 7th chords? For example, C7, F7, G7. The only one of those chords which would be directly derived from the C major scale is the V chord, or G7. Is it that the I, IV, V progression or in my example C7, F7, G7, is not actually derived from the C Major scale?