Clarky - Here's the culprit:
So to add some colour we can intercept this V-I with I sus4 [to become V - I sus4 - I]
---prep------sus------res
D major - Gsus4 - G major
----F#--------G--------G
----D---------D--------D
----A---------A--------B <-- the suspension
----D---------G--------G
Notice that the G sus4 chord contains root, suspended 4th [from the previous chord] and 5th. The suspended 4th then resolves to the 3rd.
You illustrated the Gsus4 as containg the notes G, D, A, D whereas this would be, in terms of this progression, a Gsus2. Don't get me wrong though, man - I'm not questioning your knowledge... :)
To the guy who asked about D7 containg C rather than C# - I don't know if you've had this answered already or not as I can't be bothered to read all the posts since it, but here's why:
The full name for D7 is D dominant seventh. This name comes from the classical names for the degrees of a major scale, ie. tonic, supertonic, mediant, subdominant, dominant, submediant, leading note. Usually, a dominant seventh chord is not the tonic chord of a key - it's usually the dominant chord. D7 would be the dominant chord in the key of G major - G, A, B, C, D, E, F# - and so it takes the seventh note from the key centre; hence the C natural rather than a C#.
In modal playing the dominant seventh chord can be the tonic, which is why you see it all the time in blues and jazz and stuff like that. Some scales where a dominant seventh can be the tonic are:
Mixolydian - 1, 2, 3, 4, 5, 6, b7
Lydian Dominant - 1, 2, 3, #4, 5, 6, b7
Phrygian Dominant - 1, b2, 3, 4, 5, b6, b7
There are many more, obviously, such as Mixolydian b6, the Hybrid scale, etc.
I didn't actually explain that very well at all, but I tried my best. Hopefully you understood some of it, and I'm sure someone more articulate than myslef will do better... :)
Mr Nick - Did you check out my songs yet?
JSC1 - Glad to hear it's making progress at least...
Later all - I'm off to practise for my end of term assessments.
Neil (who now has very shaggy hair that's not quite long enough to tie back because he's a poor little college student who can't afford a haircut...)
MY IUMA
