Originally Posted By: Planobilly
Thanks Eddie, I get what you are saying.

What I am saying is if you tell me we are playing in F# major and F# is the only triad used in the whole song, the key does not give me any useful information.


Sure it does, and that's where a basis in theory comes into play. There are logical places to go from the root. Picking C for the easiest example, if your root chord is C, the logical next steps on that scale are the 4th (F), the 5th (G), the minor 2nd (Dm), the minor 6th (Am), and the major 3rd (E).

I wrote a song once as an exercise, in C, where the intervals of the notes never changed. So the chord progression was C, Dm, Em, F, G, Am, G7 (with no G, just B-D-F) and then back to C.

But there's where it gets sticky. Those notes that I said made up the G7 are also the top 3 notes of a G#dim. So the theory purists would refer to that walk up a major scale as M m m M M m Dim M (octave).

So your starting chord really does give you a road map. Of course really interesting writing doesn't follow a formula. If it did every song would be so similar it would be boring. Just think of how many songs use that 1-5-6m-4 thing that Pachelbel wrote. These guys show this very well.

https://www.youtube.com/watch?v=5pidokakU4I&ab_channel=random804
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