Changes

Let's look at the intervals from two different perspectives inside the key of C Major:

{| class="wikitable"

|+ Intervals with Root Note of C

| C || B || 11 || {{M7|M7}} || Major 7th

|}

{| class="wikitable"

|+ Intervals with Root Note of A

| A || G || 10 || {{Mn7|m7}} || Minor 7th

|}

Inside any particular major scale, every note has a different set of intervals for all the other notes in the same key. In C Major, C and A both have major 2nd, perfect 4th, perfect 5th intervals but have different 3rd, 6th, and 7ths. If we added a harmony line a 3rd above the melody, we'd have a major 3rd when the melody played C (C-E), but a minor third when the melody played A (A-C).