In our previous theory lesson we learned about the concept of a scale, the difference between major and minor, and how scales can be defined as a pattern of whole and half steps.
In Class 10 we returned to this subject and talked about triads.
Some basic definitions
We can call pretty much any simultaneous combination of notes a chord.
We'll also use the term harmony interchangeably with chord. (Like many synonymous terms in this class the two words don't have the *exact* same connotations but they are close enough.)
The preferred kind of chord in most kinds of music is the triad.
I'm going to define the triad by telling you a quick and easy way to make them. Let's start with our C major scale, and look at the first five notes. If you pick out the 1st, 3rd and 5th notes from the scale and sound them together, you've made a C major triad.
If you do the same with a minor scale you will produce a minor triad.
If you superimpose a major triad and a minor triad right on top of each other you'll see that only one note is different - it's the middle note or "third."
How triads are employed in real music
The triad is more that just this little stack of notes, however. There are a few different techniques we can use to exploit them and make a nice variety of sounds.
One simple way to make different versions of a chord is to "flip it around" so that the bottom note is now on top. This makes multiple inversions of the triad.
We can run through them one note at a time, making a pattern called an arpeggiation.
We can spread them out to make a bigger, more elegant sound.
Eventually, a composer will probably want to create melodies that are based on the chords they've selected. This is actually very simple. You can start by thinking of the notes in the chord as a sort of "framework" for your tune. Plan a melody that will travel between these important tones. Use some "extra" notes to get from one chord-tone to the next and voila, you've got a viable tune.
(Here we see that a familiar childrens' melody spends all its time traveling between the notes of a single triad.)
1st, 3rd and 5th of the scale = the tonic triad
You may remember from the previous lesson that scales have a tonic or "home note." This is the tone that we begin and end the scale on, and in music it tends to function as the "most important" note.
By basing our triad on the 1st, 3rd and 5th tones of the scale, we've also found the tonic triad or "home chord." It will also tend to be a very important chord for any composition in that key. A composer has to frequently return to this harmony -- if they don't it will probably sound like the tune is in some other key instead!
However, music tends to use more than just the tonic chord. In the next part we'll look at how a key offers many different possible chords that can be combined to make an interesting chord progression.
Beyond the Tonic Triad
Each scale actually offers us a collection of chords that we can use. If we walk our triad shape up the scale it will make seven different triads of varying type (some major, some minor, one "diminished"), which we refer to with roman numerals.
In Classical music there are "rules" about which chords tend to follow which. Here is a complicated flowchart I made for one of my theory classes.
In folk music or old-school pop music one tends to rely very heavily on the I, IV, and V chords. These chords are sufficient to make most familiar tunes.
However, you don't just take our simple triad shape and move it up and down. That's considered very crude. Here is an example of the "wrong" way to play a I-IV-V-I progression:
Instead, what you do is "flip" the chords around, so that they are in the same general area and make very smooth connections. Here is our I-IV-V-I progression played nicely, with smooth connections.