Harmonizing the major scale as shown in FIGURE 8-1 also gives you the common chords for any given key. In Chapter 2, you learned about the I-IV-V progression and its use in the blues. Remember how you figured the numbering system for the chords? In the blues, you selected only three of the possible seven chords that belong to a key. The example in FIGURE 8-6 names all the chords in the key of C Major by Roman numeral.

Notice how the Roman numeral system is used to name chords. Uppercase numbers signify major chords, while lowercase numbers signify minor chords. The diminished chord is lowercase with the added degree sign (°). You saw that in the case of blues, referring to chords by numbers was integral to playing the blues progression in every key. Rock music has its standard chord progressions, too. The I-IV-V progression is found in a lot of rock music. If you ever wondered why G, D, and C chords are found in so many songs it's because G, D, and C are part of the harmonized G scale. G is the I chord, C is the IV, and D is the V.

Chords that come from the same key are related and sound good together. Try experimenting with chords from the harmonized scale in your music, and you may find some chord progressions you hadn't though of. Besides the I-IV-V chords, the progression of I-vi-IV-V is used in many older rock songs. FIGURE 8-7 is a I-vi-IV-V progression in the key of C Major.

Countless rock songs have used the I-vi-IV-V progression, and here are three:

• “Let It Be” (The Beatles)

• “All My Loving” (The Beatles)

• “In the Still of the Night” (The Five Satins)

The harmonized major scale is just one way to look at chords. It teaches the origin of chords, and while many songs use progressions out of this method, most players do it unknowingly. For many players, a I-IV-V chord progression simply sounds right; they are not aware of its origin and relation to scales.

The music of The Beatles is a wonderful place to start studying and analyzing chord progressions, because many of their songs use progressions from harmonized scales.

The important thing to remember is that theory isn't the only way. It's just another tool for you to use—something to get the job done. Many students are baffled when their favorite band's chord progressions don't come from any perceivable scale. This is fine. Music doesn't have to relate. The most important thing in the end is how the music sounds. If you like the sound, then it is good and valid. If theory doesn't work and you can't number the chords, don't worry!