In the last section, you added triads to each note in the C major scale, creating seven diatonic triads in that key. Now look at exactly what chords are created from making these triads (figure 7.11).
FIGURE 7.11 Name Those Triads
You can see from the example that a variety of triads are created. There is a major chord, minor chords, and a diminished chord. Strangely, augmented triads are missing.
The Order of Triads
The order of triads in the scale is important. In a major scale/key, the triads always progress in this order: major, minor, minor, major, major, minor, and diminished. Memorize this order; it's going to serve you quite well—and the best part is that what you've just done in the key of C major holds true in every major key. Since all major scales are constructed in the same fashion, with the same intervals, when you stack triads in any major scale, you always get the same order of triads/chords. This is a huge time-saver! Only the names of the notes change because no two keys have the same pitch. The chords and their order will always be the same.
FIGURE 7.12 shows an example of this order of triads in the key of D major, B major, and E major. The figure illustrates that no matter the scale, the same order of triads always exists. Just as major scales have formulas for their construction that allow you to spell any scale easily, knowing that the triad order holds true to all the keys is a dependable element in music theory.
Notice that the notes in the scales are in different keys, but the order of chords (major, minor, minor, major, major, minor, and diminished) stays the same. This holds true for every major scale/key.
To music theorists, there isn't any real difference between any major key. Unless you have perfect pitch, so you can name a note just by listening to it, you won't be able to hear a difference between C major and D major scales. Since there is such equality in the keys, music theory has a system of naming chords relative to the note of the scale from which they are built. If you were to number the notes and their corresponding triads from the G major scale, you'd end up with the image in FIGURE 7.13.
FIGURE 7.13 Numerals with Triads
Since triads are built off the notes, they can be referred to by a number and/or Roman numeral. For example, a one chord in the key of C major is the chord built off the first note in the scale, which is C major. Since every major scale starts with a major triad, the one chord in any major key is major.
In Chapter 3, you learned the names of the scale degrees. When discussing chords, the scale degree names are used as well. I (one) chords are referred to as tonic chords, while V (five) chords are referred to as dominant chords. This corresponds with the information in Chapter 3 on the proper names for scale degrees.
The only limitation is that there is no way to convey whether that chord is major or minor simply by using the number 1, 2, or 3. Musicians use Roman numerals instead of Arabic numbers for this very reason. You may remember from math class that Roman numerals have lowercase equivalents. By using uppercase Roman numerals for major chords and lowercase Roman numerals for minor chords, musicians have created a system that makes sense in every key and conveys a lot of information about a chord.
FIGURE 7.14 shows the harmonized major scale with the corresponding Roman numerals. Notice that the diminished chord is denoted by a lowercase Roman numeral and a small degree symbol next to it. That's the standard way to indicate diminished chords.
FIGURE 7.14 Major Scale with Roman Numerals to Indicate Chord Quality
Roman numerals are a standard way for music theorists not only to name chords, but also to analyze choral structures in pre-existing music in order to gain some insight into how the music was constructed. Roman numerals are still a convention in classical music. If you plan to study music formally, you need to know Roman numerals.