The Complete Idiot''s Guide to Music Theory

Part 1:
Tones
For example, every C scale starts on C and ends on C; an F scale starts on F
and ends on F; and they all have six more notes in between.
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The eight notes of a scale; C Major, in this instance.
The first note of a scale is called the tonic, or first degree, of the scale. Not
surprisingly, the second note is called the second degree, the third note is called
the third degree, and so on—until you get to the eighth note, which is the
tonic again.
The major exception to the eight-note scale rule is the scale that includes 
all
the notes within an octave, including all the sharps and flats. This type of scale
is called a 
chromatic scale, 
and (when you start with C) looks something like this:
The C chromatic scale; the top staff shows the scale using sharps, the bottom staff shows the scale
using flats.
Now, any given scale has specific relationships between the different degrees of
the scale. That’s how you can describe different types of scales: A major scale
has different intervals between specific notes from those you’ll find in a similar
minor scale. These different intervals give each type of scale its unique sound.
The most common scale is called the 
major
scale. Major scales are happy scales;
they have pleasant and expected intervals at every turn. (Just sing “Do Re Mi Fa
So La Ti Do” and you’ll hear this pleasant quality.)
The mirror image of the major scale is the 
minor
scale. Minor scales are sad
scales; the intervals between the notes sound a little depressing.
Both major and minor scales can start on any note—from A-flat to G-sharp. No
matter which note you start with, each scale has its own specific combination of
intervals between notes.
The following sections go into more detail about both major and minor scales.
Major Scales
What makes a major scale major are the specific intervals between the notes of
the scale. Every major scale uses the same intervals, as shown in the following
table.
Most musicians
don’t capitalize the word
“minor,” or any of its
abbreviations. Major chord
notation is (almost) always
capitalized, and minor
chord notation is (almost)
always lowercase.