The_Complete_Idiot%27s_Guide_To_Music_Theory

118
Part 3: Tunes
Minor seventh chords.
For example, a C minor 7 chord includes the notes C, E♭, G, and B♭.
Here’s a quick look at how to build minor seventh chords on every note of the
scale:
There are several ways to indicate a minor seventh chord, as shown in the following
table:
Notation for Minor Seventh Chords
Minor Seventh Chord Notation Example
minor 7 C minor 7
min7 C min7
m7 Cm7
Other Sevenths
When I said there were three basic types of seventh chords, I left the door open
for other types of less frequently used seventh chords. Indeed, you can stick
either a minor or a major seventh on top of any type of triad—major, minor,
augmented, or diminished—to create different types of seventh chords.
For example, a major seventh stuck on top of a minor triad creates a “minor
major seventh” chord. (That is, the base chord is minor, but the seventh is
major.) This is notated 1-♭3-5-7; a C minor Major 7 chord would include the
notes C, E♭, G, and B (natural).
Other types of seventh chords.
A minor seventh on top of a diminished triad creates a diminished seventh
chord, like this: 1-♭3-♭5-♭7. (This is the chord you get if you play a seventh
chord based on the seventh tone of a major key.) A minor seventh on top of an
augmented triad creates an augmented seventh chord, like this: 1-3-♯5-♭7. A
major seventh on top of an augmented triad creates a major seventh chord with
a raised fifth (♯5), like this: 1-3-♯5-7 … and so on.