dcocharro wrote:You can think of 9ths, 10ths, 11ths...... as extra tension added to chords. When these notes have this kind of role, usually you don't find them in the same octave of the root.
If you look at the scale 9, 10, 11 are equivalent to 2nd, 3rd, 4th of the scale and so on...
The C6 can be thought as the first inversion of the Am.
I think of them in a new way now I really find helpful - as in some situations you wont know when or how to write an 11th chord etc. So this will help song writing.
Think of it this way - in traditional song writing terms - when writing a piece of music, people usually start writing a simple chord progression. (writing a melody and then harmonizing gives far more interesting results when you know how, but we'll stick with this) Then probably write a melody on top of the chords.
Generally we dont always want the melody to land perfectly in consonance with the chord on the 1st beat of a given bar. We want suspension or dissonance to keep interest in the melody, otherwise everything becomes predictable and bland. http://en.wikipedia.org/wiki/Consonance_and_dissonance
So we choose a note that isnt part of the chord for dissonance, and then resolve it on the 2nd beat or thereabouts. 7ths, 9ths, 11ths, 13ths, sus4, 6 are all just naming conventions for the different types of dissonance we can have on any given chord.
Take for example the chord C major in the key of C major - notes are C, E, G.
Right, so we might want to add a bit of suspense to the chord and avoid using one of the chord tones notes with our melody. (these all apply to the highest notes) So notes we have left -
D - 9th (a full octave and a 2nd above the tonic note - C is the tonic in this case)
F - 11th (An octave and a 4th above)
A - 13th (An octave and a 6th)
B - major 7th
Then, if the melody is closer to the tonic, you have suspensions -
F - (suspended 4th, replacing the 3rd - your ear will want it to resolve by falling to the 3rd of the chord)
Then various inversions and so on.
So remember - chord additions are simple just ways of describing the various dissonances possible within a chord, and are 'usually' describing the melody. They are vital to keep interest and the music moving.
If youve ever seen a chord book of any band (the beatles are an easy example) the chord boxes they give above the music generally arent what the band play - they are the piano/guitar chords plus the melody. John Lennon is probably playing a normal G chord, but is signing a 'A' on top of it on the 1st beat, so the chord in total (as you have to take in account all the music going on) is a G9.
If you get the balance between dissonance and consonance just right, youll have a great melody to work with.
Anyways, hopes this helps some people figuring out when and where to use these chords. If their melody is any good, theyre probably using them already. Just people forget vocal melody or synth melody is still part of the chord.