#1
Hi,
I know it may not be that revolutionary, and it was probably already known back in the XIX th century, but I found this :

If you write a chord progression where each chord is a relative 3rd higher than the previous chord, you only have to change one note of your 3-note chord, at each progression, to keep your 1-3-5 chord.

OK it's not clear. Here's an example :

1st chord : I : Em (E-G-B)
2nd chord : III : G (G-B-D)
3rd chord : V : Bm (B-D-F#)
4th chord : VII : D (D-F#-A)
5th chord : II : F#5- (F#-A-C)
6th chord : IV : Am (A-C-E)
7th chord : VI : C (C-E-G)

This makes for interesting chord progression and momentum gain.

The inverse pattern is also possible, instead of a 3rd higher, go a 3rd lower (a 6th), and instead of going down, the progression will be higher and higher.

Well...
#2
You're right; people did find this out earlier than both you and I have been living.

http://en.wikipedia.org/wiki/Tonnetz

I learned about it in college and it's pretty darn useful if you ask me.
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#3
Hell yeah!!! That's what I'm talking about!

"described in 1739"

I was underestimating the age of this "theory thing" haha!

Anyway, it's still a discovery for me

Thanks for the link!