Practical Music Theory unit 7: Chord Scales (triads)
Chord Scales - triads
Chord Scales (triads)
A “Chord Scale” refers simply to all of the basic chords that are available in a given key or mode. You can refer to the Table Of Major Scales to see the other keys, but for the following examples I’ll use the key of C Major. This time, we’re going to number each step of the scale using Roman numerals–this is the common practice for identifying chords within a scale. And I wrote out two octaves of the scale–you’ll see why in a minute.
The I chord: major
Using the concepts covered in the lesson on chord construction, we build a chord from each step of the scale. The first chord, built from the first step of the scale, is known as the I chord (that’s a Roman numeral 1, so we just call it the “one” chord).
We know that if we take the 1st, 3rd, and 5th steps from a major scale as-is, without flatting the 3rd or 5th, we have a major triad. This will be true for any major scale in any key–the chord built from the first step of the scale will be a major triad. So, we can say that “the I chord is major.”
The II chord: minor
Now we’re going to move to the second step of the scale, so in this case D. We then apply the same concept to build a chord from this step:
We know (refer to the table of major scales if you need to) that a D major triad is spelled as D-F#-A. But in this case, we have D-F-A (no F#). In other words, the 3rd has been flatted (lowered from F# to F). You may remember that a flatted 3rd gives us a MINOR triad. Again, this will be true for ANY major scale. Therefore we can say, in general, that in a given key, the II chord is minor.
The III chord: minor
Now let’s build a chord from the 3rd step of the scale, the E:
We know that an E major triad would be spelled E – G# – B. But building off of the E in this scale, we get E – G – B. So, again, the 3rd has been flatted–lowered from G# to G. This gives us another minor chord. So we can then say that the III chord is minor.
The IV chord: major
Now let’s look at the chord built from the 4th step of the scale (and now you can see why I wrote out two octaves of the scale):
An F major triad is spelled F – A – C (refer to the Table of Major Scales if you like). And when we build from the 4th step of a C major scale, we also come up with F – A – C, a.k.a. an F major triad. Therefore we can say that the IV chord is major.
The V chord: major
Now we’ll look at the chord built from the 5th degree of the scale:
A G major triad is spelled G – B – D, and when we build the chord from the 5th step of the C major scale, we also get G – B – D. Therefore we can say that the V chord is major.
The VI chord: minor
Now build the chord from the 6th step of the scale:
An A major triad would be spelled A – C# – E. When we build the VI chord from the key of C, we get A – C – E. So the C# has been lowered (flatted) to a C. Like we saw with the II and III chords, this means we have a minor chord. Therefore we can say that the VI chord is minor.
The VII chord: diminished
Finally, we’ll build a chord from the 7th step of the scale:
A B major triad would be spelled B – D# – F#. But in this case, we get B – D – F, so both the D# and the F# have been flatted to just D and F. Remember, from the lesson on chord construction, that a flatted 3rd AND a flatted 5th together make a diminished chord. So we say, then, that the VII chord is diminished.
Recap-the “chord scale” for C major
So, going through all seven steps of the C major scale, and building triads from them, we get the following chords:
This is known as the “chord scale” for C major. Note that these are the triads–the next lesson will cover seventh chords.
The chord scale in any key
Like I have mentioned, we can take what we learned in this lesson, and apply it to any major scale, and come up with the following generalizations for all keys:
I chord = major
II chord = minor
III chord = minor
IV chord = major
V chord = major
VI chord = minor
VII chord = diminished
Be aware that you are by no means limited to these chords when you’re playing in a given key. These are just the most basic chords that can be derived from the key. But it’s entirely possible to have chords in a song that do NOT follow what we have learned here, so don’t be surprised when you run into it.