Originally Posted by: adamstocker

Thanks for the response, would you mind giving and example on each point you mentioned please to cement my understanding? Thanks.

Jarkko's reply is a quick, handy way to look for relationships among chord groups. Because all major scales have the same interval formula, harmonizing every one of them always results in the same relationship of chord qualities.

I (1) chord is always major

whole step up there is always

ii (2) chord is always minor

whole step up there is always

iii (3) chord is always minor

half step up there is always

IV (4) is always major

whole step up there is always

V (5) is always major

whole step up there is always

vi (6) chord is always minor

whole step up there is always

vii diminished (7) chord is always diminished

half step up is

I (1) chord is always major

Examples!

If you have an A major chord and a B major chord in a progression, those are 2 major chords a whole step apart. They must be the IV & V chord in E major.

If you had C major & D major, those are 2 major chords a whole step apart. They must be the IV & V chord in G major.

If you had D minor & E minor, those are 2 minor chords a whole step apart. They must be the ii & iii in C major.

All this is covered in my tutorial on harmonizing the major scale. Hope that helps!