Time for a brief resume.
If you followed this thread, you should now be able to build close position major and minor triads all over the neck on all sets of 3 adjacent strings.
You should as well be able to go from any plain major/minor chord to the next with as little movement as possible. Which obviously isn't always mandatory musically - but very often it's a great way to build "plausible" chord movements with proper voice leading.
IMO this can take you quite far already - the few examples I've posted are really only scratching the surface (at least so far).
And the most interesting things are yet to come.
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Something else: The attentive folks may now ask: "Hold on, what about that diminished triad?"
Yeah, what about it? Possibly deserves a little bit of explanation.
First off: Any chord not using (or suitable to use) a perfect fifth (the interval 7 semitones away from the root) is generally considered "unstable". It's hardly ever a chord you may land on to finish something, let alone being the "home" (aka tonic) chord for whatever composition. Yes, I know that there are exceptions, but in 99.9999% of typical western culture based music there's no exceptions.
In many (possibly the majority of) cases, the diminished chord is used as a kind of substitute, extension, placeholder - or whatever you may call it - of something else. Jay has actually already mentioned a pretty typical use case, namely a diminished chord building up on the third of a major chord, resulting in a "final" sound of a dominant seventh chord.
Example: A spelled out C7 chord would be C-E-G-Bb. And when you look at the notes starting on the third E, it's E-G-Bb, an Edim triad. Now, when you play this chord and have it resolve to, say, an F major triad, the impression will be that of a C7 chord being played, regardless of whether there's actually a C root note present or not. Great stuff.
There's certainly other use cases, too - but this is likely the most common one. And in general, it could rather safely be said that the diminished chord usually can't "live on its own".
And while we're at it, this kind of "let's place a triad (not just a diminished one) over another root note" thinking is absolutely interesting and something I will defenitely get into later on.
But for now, I think it's pretty safe to skip the diminished chord for a while (poor fellow - grow a pair, err, a proper fitfth next time).
And if you still wanted to construct any diminished triad right now, that's easy. Just lower the 5th in any of the already examined minor triads and there you go. A-C-E (Amin) becomes A-C-Eb (Adim).
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Another thing I wanted to mention: You may have noticed that I'm largely using the D-G-B strings. I think that these are the best working set of strings on pretty much any guitar. Sort of full sounding without getting muddy, sort of sitting well in mixes (of course that depends on a lot ot other things, too), sort of cutting through without getting harsh.
In addition, I think of that string set as offering the best balance in case you want to add stuff. There's the E1 string in case you want to have something on top and the A5/E6 strings in case you needed to provide lower root notes on your own.
Further, for me, most things are playable easily on these strings.
YMMV, but that's like it for me.
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Next: The cheesiest cowboy chord backing I could possibly come up with. Which will hopefully get some sort of "let's make this at least a more delicious cheese" treatment, just using the things explored so far.
Edit: Link to next "content" post.