Seventh chord

The seventh is almost always flatted when seventh chords are used in popular music. Thus, a C7 chord would be C - E - G - Bb.

When playing a seventh chord from a fake book or lead sheet on a keyboard instrument, you generally leave the root tone out of the right hand part, replacing it with the seventh. Then play the root tone with the left hand.

When used excessively (especially uninverted), seventh chords can make your composition sound like 70s porno music or terribly, terribly hackneyed (for instance, try leading from a G7 to a C chord, and tell me if it could ever sound exciting). However, used judiciously, they can be truly graceful.

Seventh chords can be analyzed using a two-word description, where the first word corresponds to the size of the triad (the first three notes in the chord), and the second word corresponds to the size of the interval between the bottom note and the top note (which will always be a seventh of some sort, called the 'outside' seventh).

An example: Major-minor is probably the most common type of seventh chord; the dominant seventh chord in a major scale is Major-minor (abbreviated M-m; a capital M stand for Major, and a lowercase m stands for minor). In C Major, the dominant seventh chord is G-B-D-F. The bottom triad, G-B-D, is major (see triads for explanation), and the outside seventh, G-F, is minor, so G-B-D-F (G7) is a M-m 7th.

Other types of seventh chord include: minor major seventh, minor seventh (minor triad-minor outside seventh), major seventh (major-major), half-diminished seventh (diminished-minor), and diminished seventh (diminished-diminished).

Alright, first of all...
In any Diatonic Major key there is only One dominant chord. That is the five chord - or V7 in traditional nomanclature. Dreamword is using the dominant 7 as every seventh chord, instead of appopriately alternating between the seventh chords listed above by Eliah. Instead of using the dominant 7 everywhere you want a 7th chord, use the major 7, or minor 7, appropriately. Like this: Cmaj7 Emin7 Fmaj7 Dmin7 G7 Cmaj7

Dreamword seems to be confusing the use of seventh chords in ordinary songs with the use of sevenths in the Blues form. in the Blues, all chords are dominant 7ths, even though this makes it not a diatonic key. Also, funk often uses dominant 7ths exclusively, but that is a much looser rule.

It's understandable, tho... Most cats will call a "Dominant Seventh" chord simply a "Seven" chord for short.

Using seventh chords can add a deepness to your music that typical triads cannot. Minor chords can sound darker, major chords can sound brighter... then throw in inversions, and you'll get minor chords that Sound major, and other such wacky oddities. Memorize what chords are diatonic in each key, and you'll learn to substitute regular triads with the appropriate diatonic seventh chord with much less thought. Its not as easy as lowering the root a whole step, but it is not impossible. It is fundamental to any jazz player, or any well educated all-around musician. So get it right, goddammit... just kidding... goodluck.