Buleriachk wrote:Lessee now:
Tritone substitution:
http://en.wikipedia.org/wiki/Tritone_substitution
Standard Blues Turnaround
(C -> B7)-> E Blues turnaround (B7 resolves to E)
B is the dominant to E; dominant 7th to tonic in E Major
Tritone substitution (E Major)
Changing the dominant 7th to a "tritone substitution" B7 -> F7
(C -> F7) -> E
(F7 doesn't have a Bb note in it last time I looked, anyway).
You are confusing yourself. Slow down and study it all carefully if you truly wish to learn about it.
The definition (from memory and without the aid of your Wiki link) of a tritone substitution is the substitution of a dominant 7th chord by another dominant seventh chord whose root is a tritone away from the root of the original dominant seventh chord.
So the dominant of B is F#, spelled F#-A#-C#-E.
The dominant seventh chord whose root is a tritone away from F#7 is C7, spelled C-E-G-Bb.
You'll notice that the reason these two chords can substitute for each other is that their 3rds and 7ths share an inverse relationship. A# is the 3rd of F#7 which becomes Bb as the 7th of C7; E is the 7th of F37 and becomes the 3rd of C7.
A tritone substitution can happen on any dominant resolution, not only as an alteration of the V chord in a ii-V-I.
So back to your initial example, a C7 moving to B7 is a tritone substitution because the C7 is substituting for an F#7, which is the dominant of B7.