Originally Posted by: zreynoldspI throw in the occaisional 7th - 7th chords tend to fit with standard major & minor fairly easily. Diatonic Harmony for Major chords and 7ths is the same except in 7ths the fifth scale degree is dominant, where in standard major it's major.
9th's are trickier as you'll find the added ninth often doesn't come from the key you're playing in, so it sounds wrong. Sometimes this can work anyway, but they almost always sound 'outside' to me.
If anyone has the secret on ninth's, I'd like to hear it too! :D
I've substituted add9 chords in standard progressions before, and that works well for a different sound...
This is wrong.
You should know that a 7th and a 9th are extensions of a triad. The extension name and chord is not based on the scale so much as the chord and key signature.
Lets cover some ground first:
It helps to think of a musical staff instead of your fret board. The theory is based off of the staff. The type of interval (the root, 3, or 5) is determined by the staff. Words like Major, minor, augmented, or diminished are derived from the number of half steps or whole steps on your instrument.
The triad is a root 3rd and 5th. By definition its a 3rd stacked on top of another 3rd. These are your basic barre chords.
The root for a specific chord never changes
The 3rd can be either major or minor. Occassionally it might be augmented or diminished. However in a major scale and its relative modes the thirds are always either major or minor.
Every diatonic 5th is perfect (meaning to never change.) The exception to this rule is a chord whose root falls on the 7th degree of a major scale. The chord that falls on the 7th degree of a major scale always contains a diminished 5th.
Triads In a nutshell...
...There are 4 basic types of triads:
Major (1, 3, 5)
Minor (1, 3m, 5)
Augmented (1, 3, 5aug)
Diminished (1, 3m, 5dim)
When you are playing an extension of a 7th chord all your doing is adding another 3rd to your triad.
In the major scale, only two chords have a major 7th. The first degree of the scale (or tonic) is a major 7th. The 4th degree of the scale (or subdominant) is a major 7th. These chords are major triads with a major 7th added to them. The seventh is a major 7th in relation to the root, not its preceeding 5th.
Three chords in the major scale are minor 7th chords. The chords are build on the 2nd 3rd and 6th scale steps (also called modal steps.) A minor seventh chord is a Minor triad with a minor 7th added to it. The 7th is a minor seventh in relation to the root, not its preceeding 5th.
There is one dominant 7th in the major scale. It falls on the 5th scale degree (also know as the dominant scale step.) The dominant 7th is a major triad with a minor 7th added to it.
The last diatonic 7th falls on the 7th degree of a scale. Its called a Half-diminished 7th. Its a diminished triad with a minor 7th added to it.
Altogether there are 7 different types of 7th chords. The other three are non diatonic. And I dont remember them, sorry.
Ninth chords employ the same concept as the traid and 7ths. You just add another 3rd to the 7th chord that you are already playing.
9 - 7 = 2 (the 7 comes from the amount of diatonic notes that fall within an octave without counting the octave.)
What this equation tells us is that the 9th of a chord is the chords 2nd + an octave.
So for a 9th chord based on the 1 degree of the scale, you would play a major triad plus a major 7th plus a major 9th. But for a 9th chord based on the 3 degree of the scale you would play a minor triad + a minor 7th + a minor 9th. The ninth is minor because the interval from (in scale degrees) the 3rd to the 4th is a minor second. In terms of scales, the 3rd has an interval of a minor 2nd, and the 7th has an interval of a minor 2nd. The rest of the scale steps have intervals of major 2nds. 2nds translate to 9ths.
I am not familar with the different names of 9th chords or the rules to naming them. But I am pretty sure that there are 21 9th chords. Some of them dont sound like ninths though, some sound like inversions of different chords.
If your asking when in the song structure or when in time (the arrangment) to play 9th chords and 7th chords, thats more of an artistic then theoretical idea.
A lot of blues and jazz songs play only 7th chords and exentions based on those (like 9ths.)
Alot of rock songs play strictly triads or even less (double stops (intervals.))
Bass guitar is the answer to everything
