I think everyone has answered you question Afro.
"Why dopes a Gmin6 contain a Major sixth instead of a minor sixth?"
Gminor - To create a Major, Minor, Augmented, Diminished, Anything chord, we take the
Major scale. Yes, the
Major scale,
NOT the minor, and slap the Major scale pattern onto the root note. In this case G is the root, hence G Major.
Once you can forget about following the minor scale and sticking with the Major, this may be repetative, but just look it over quickly then,
Now, to create a
Major sixth, we have the triad (Intervals 1, 3, 5) and add a 6th from the Major scale pattern:
W W H W W W H
1 2 3 4 5 6 7 8
G A B C D E F# G
^ ^ ^ ^
We now have a P1, M3, P5 and M6,
E|-----------------------|
B|-----------------------|
G|-4------4-----------4--|
D|-2--------------2---2--|
A|-5----------5-------5--|
E|-3--3---------------3--|
P1 M3 P5 M6
Creating a Minor triad Chord is simply done by flatting 3rd, also known as a Minor Third. You do not move the sixth down a half step like you do with Seventh Chords (minor 7th - P1 m3 P5 m7, Major 7th - P1 M3 P5 M7, Dominant 7th - P1 M3 P5 m7).
So we have a minor 6th with a P1 m3 P5 M6
E|-----------------------|
B|-3----------3-------3--|
G|-3------3-----------3--|
D|-2--------------2---2--|
A|-----------------------|
E|-3--3---------------3--|
P1 m3 P5 M6
We have a M6th because it's THE sixth of the scale, adding a minor sixth(D# {Eb}) into the chord we created makes a Major 7th - G D# A# D, (the resoan this happens? probably some math thingy)
D Maj 7th
E|(3)----(3)---------(3)-|
B|-3-------------3----3--|
G|-3----------3-------3--|
D|-1--1---------------1--|
A|-----------------------|
E|-3------3-----------3--|
P1 M3 P5 M7
Does this make sense? I hope it helps.
