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Here are some important ideas. A scale is any collection of notes into which we divide a fundamental interval that we have come to call an “octave.” An octave interval is the difference where the higher pitch is exactly twice the frequency (cycles per second, or Hertz, abbreviated Hz) of the lower note.
In what we call “Western Music,” we divide that octave interval into 12 tones. Take a look at a piano or any other keyboard. There is a repeating pattern of white and black keys. All the white keys have letter names, A through G. There are seven white keys before the pattern repeats, starting the next octave. The black keys are the “in-between” tones that we designate with either sharps or flats, depending on the “key” of the music.
12 frets define an octave on a guitar. Pluck any open string, then play the same string fretted at the twelfth fret. The string will vibrate twice as fast and the nite will sound an octave higher. (It is not a coincidence that the twelfth fret is halfway between the nut and the saddle – that just physics of mechanical vibrations!) The musical difference in pitch between adjacent frets on a guitar corresponds to the pitch difference between adjacent keys on a piano.
“Key” is an important concept you will learn in Fretboard Wizard. It is the name of the note toward which the song pulls or “resolves,” and most songs end on the note that names the key. It gives a real sense of completion or arriving “home.” Songs that end on some note other than the key leave a sense of unfinished business or suspense, sort of like an unanswered question.
If we use all 12 piano keys or guitar frets in order, we call that a “chromatic scale.” But rarely does music use a full chromatic scale. Chromatic runs are sometimes used as an embellishment in parts of a melody, but most of a composition usually uses a smaller subset of pitches for the “scale” to which the music is set.
Two of the most common scales are the “major scale” and the “natural minor scale,” each consisting of seven of the 12 pitches. In FW, you will learn that the natural minor scale derives from the major scale, using the same tone but just using a different starting point for the “home” that defines the key center.
So if we select only seven if the 12 tones, how do we know which ones to pick? The intervals between adjacent tones in any major scale always have the same relationship, regardless what key we have.
Let us start by defining whole steps and half steps. The smallest interval on a piano is two adjacent keys. The smallest interval on a guitar is one fret. These have exactly the same significance. We define a whole step as a difference of two frets (or two keys on the piano), therefore a half step is just one fret.
Now, all major scales have the pattern W-W-H-W-W-W-H, where w = Whole and H = Half. Let’s think only about the white keys on a piano. If you you are not familiar with the names of the keys on a piano, browse that on the web. The major scale that uses only white keys is the key of C. The “relative” natural minor scale that uses the exact same keys is A minor, and it begins on the same note that is the sixth step of the C major scale, namely A. I’m going to wrap this up by saying that the pattern of notes for the natural minor scale is therefore W-H-W-W-H-W-W. Hopefully this diagram brings it home:
(Edited to add: Naturally my diagram is a failure because of the editing software. What you see when you compose is not what you get when it posts. I will illustrate the old -fashioned way and then post a photo. I just hope it will allow me to do that.)
C major: C D E F G A B (C)…
Interval: W H W W H W W W H
A minor: A B C D E F G (A)…
The pentatonic scales choose only five of the notes. (Pentagrams have 5 sides.). The A minor pentatonic uses A-C-D-E-G(-A), where the A in parentheses denotes the beginning of the next octave). The C major pentatonic uses C-D-E-G-A-(C). Again, these two scales use the same notes, simply with a different starting point that defines the key center or sense of “home.”