Rick Mabry quotes from an article by Ian Macdonald:

>"The Seventh Symphony is a fascinating instance of Vainberg and
> Shostakovich treading so closely in each other's footsteps that
> it is hard to distinguish who is following whom."

I went to the web site cited by Rick and it was indeed foscinating.
In my as always humble opinion the key to the whole S V entanglement
is that they lived on the same block in Moscow.  I picture S going to
V's place (or the other way around) late at night and asking: do you
have an adagio I can borrow (from?) A detailed article on this subject
will be submitted to the Journal of S and V Studies.

Bernard Chasan