I come from a strong engineering background and the learning methods for us left brainers are significantly different then most really good musicians who are "traditionally" right brainers, although there are always exceptions to the rule.  Those of us who view the world from the left side of the brain need to see the whole picture and how everything fits within that whole.

As someone who has that exact same background and has that same "why" need, the book that cracked it open for me was "Scales over Chords" by Wilbur Savidge.   It is based on the CAGED method, which should make complete sense to your left brain.

When I made the original post I was going through the book and videos associated with Fretboard Theory by Desi Serna.  I consulted with him on this and he confirmed that my description is correct when you are starting from scratch in writing a song.  Of course the opposite would be true on an existing song.

I just wanted a very high level understanding of what Mode is and how it interacts with Chords, Keys, and Melodies. 

I come from a strong engineering background and the learning methods for us left brainers are significantly different then most really good musicians who are "traditionally" right brainers, although there are always exceptions to the rule.  Those of us who view the world from the left side of the brain need to see the whole picture and how everything fits within that whole.  Right brainers approach things very differently...   Again, I am not saying anything about those who have right brain views.  But if you read the thread, you can see there are a variety of views about how to go about this subject.  Again, I am not saying anything is wrong with that. 

This is just how I need my left brain centered mind to go about understanding how Modes fit into the entire picture.

I can't do maths either.

Here's an analysis that applies to SBR. Might skip to the part that talks about lowering the root."

Did you intend to attach a link?

Here's an analysis that applies to SBR. Might skip to the part that talks about lowering the root."

For example, I pretty much get the whole 1-4-5 thing and can usually hear it when I listen to songs.  But I sometimes get thrown off when I hear a song such as the Eagles' version of "Seven Bridges Road".  The progression in the verses is:  D - C - G with resolution back to D (1-b7-4).  So the song is in D, but it obviously doesn't follow the 1-4-5 pattern.

One could argue that it's in G, which would follow the 1-4-5, but my ear recognizes that the D is the "home" chord.  (Would that be what you'd call the tonic?)

Your explanations help.  Thanks again.

PS:  Apologies to the OP for threadjacking.

***EDIT:  This conversation seemed familar, and it turns out that it was:

http://www.chordie.com/forum/viewtopic.php?id=19937

In fact, the whole notion of modality is better thought of in terms of melody and scales vs. chord progressions. Consider a blues song in C that goes:
C7       F
C7       F       G

When we talk about what key that song is in, we say C or C major. You wouldn't generally say "it's in the key of C mixolydian" because "C mixolydian" isn't a key. It's a scale.

However when I'm jamming with my guitar buddies I might say "here are the changes. Think C mixolydian when you're soloing."

I would find some chords that sound good with the melody you have chosen and not worry about the mode

Well . . . maybe.  Upfront disclaimer:  I know squat about songwriting.

Having said that, it seems to me that Russ would be right assuming that USMC has a melody already "chosen".  That's not necessarily a valid assumption.  Maybe the intent here is to find a nice chord progression within a particular mode of a particular key.  Once that is established, then work on harmony and melody lines using the appropriate scale to go along with the chords.

I would think that is how a lot of songs are written, i.e. chords first, followed by melody.

But like I said, I know squat about it.

I would find some chords that sound good with the melody you have chosen and not worry about the mode

Amen!

I am new to music and trying to make sure I understand the concept of how modes work in the greater scope of guitar. I am looking for someone to look at what I think I understand and confirm or correct it.

A greatly simplified song…

[*]We start with determining the [B]Key[/b], which provides us with the [B]Scale[/b].
[*]Then we determine the type of tone we want [B](Mode)[/b] by choosing one of the degrees (I, ii, iii, IV, V, vi, vii) from our scale as our central tone/root chord. We play the root chord in a progression which provides the [B]Harmony[/b] and make sure the root is the dominant tone.
[*]Then we overlay the harmony, with the notes from the original scale which makes the [B]Melody[/b].

I am just looking for a high level confirmation that what I have defined above is correct.

Thanks