How to Name Notes, Scale Degrees, and Chords on the Guitar
The notes of a scale are usually numbered 1st, 2nd, 3rd, and so on. You use Arabic numbers when you’re talking about the notes themselves and Roman numerals when you’re talking about the chords built on those notes. So in C major, 3 or the 3rd is the note E, and iii is the chord E-G-B.
The different scale degrees also have names. Dominant refers to the 5th scale degree. For example, G is the dominant of C major, and B is the dominant of E major. Here’s a complete list of the names for the different scale degrees:
|7||Leading note or leading tone|
You can also call the V chord a dominant chord. For example, the dominant chord of C major is G-B-D.
There are a couple reasons why V resolves so well on I. Understanding these reasons requires you to examine the intervals within a V chord to see how they relate to chord I. This involves taking a look at the leading tone and the tritone.
How to lead with the leading tone on the guitar
As a listening experiment, play up a major scale, starting from the tonic note, but instead of playing a full octave, stop on the 7th scale degree. Using C major as an example, play up the scale from C to B and hold on the B. The scale sounds incomplete: The B wants to lead back to the C to sound complete.
This is why the 7th scale degree is also called the leading tone or leading note of a scale.
If you turn to the pitches of the V chord, you find that it contains the leading tone of its parent scale, which is why it has such a strong tendency toward I. For example, the G chord is made up of the pitches G, B, and D — its root, 3rd, and 5th. The 3rd of the chord is a B, the leading tone of C major.
Basics of the tritone on the guitar
To intensify the tendency for V to lead to I, simply add a 7th to the chord, making V7. This added pitch comes from the 4th degree of a major scale. The interval from the 4th to the 7th of a major scale is an augmented 4th, while the interval from the 7th back up to the 4th is a diminished 5th.
Both of these intervals are made up of three whole tones and can be called tritones, which, not surprisingly, means three tones. Examples of tritones are B-F in C major and Gs-D in A major.
When you play these examples of tritones, you can hear that a tritone is a fairly unstable, or dissonant-sounding, interval. As a matter of fact, it sounds so unstable that when it appears in a chord like V7, the chord itself has a strong tendency to move to a more stable one.
For example, the B and F of G7 want to move to the C and E of C, and the Gs and D of E7 want to move to the A and Cs of A. Here are two versions of a G7 chord, with the tritones shaded in black. Follow each one of these chord shapes with a C chord and you hear resolution.