These things are by definition available in every key. Count upward from the root chord (e.g. "D" in the key of D), counting it as "I." The "IV" chord is therefore G, and the "V" chord is A.
Each chord is in its simplest form a triad, consisting of the first, third, and fifth notes from its root. You can add additional notes: the seventh, ninth, even the eleventh ... the latter two of which have proceeded into the next higher octave. The fourth and sixth notes are also available. Each and every one of them offers a different tone. ("The second" produces a dreadful train-wreck clash.)
The "sus" term, for "suspended," generally refers to the progression of one chord to the next. For instance, a "sus2" note is "suspended over" from the previous chord and "resolved" in this one. In such chords, the third is omitted so that it does not clash with the suspended note (2nd or 4th).
I'm a little reluctant to delve into too much "music theory stuff" here, but there are also "tone colors." Start with the "C major" triad (C-E-G), and now: "Play E-flat ("flat third ..."), instead." You get "C minor." Flatten both E ("the third") and G ("the fifth"), and you get "C diminished." Go back to the original chord and play "G-sharp" ("sharp fifth"), and you get "C augmented."
The (mumble, mumble ... you can stop reading now ...) technical reason for this magick is that "a triad" actually consists of two adjacent intervals. Quite literally the distance (in "keys on the keyboard, white or black") between "C and E," and between "E and G" in a C-anchored triad. When adjacent intervals of different "distances" are sounded together in a single chord, these "colors" are produced. (Okay, that's enough "theory" to get you started.)
If you don't mind a rather-intense textbook, songwriter Jimmy Webb wrote a book called Tunesmith, and the "middle eight" of that book is quite literally a textbook which thoroughly discusses this and many other topics. I've read my two now-autographed copies carefully through about six times so far and I've learned something new every time ... but, "it is for the brave of heart."
And ... there's a tremendous amount of material out there, all over the Internet. Happy Googling!
(There's even cartoons(!) – I kid you not – at "tobyrush.com!")
Last edited by MikeRobinson
on Tue Jan 12, 2021 11:50 am, edited 8 times in total.
"I wanna quit being a computer consultant and become a composer and arranger at age fifty-nevermind."
Logic Pro X, MacBook Pro, 88-key MIDI controller.
Just south of Chattanooga, Tennessee, USA