Thanks - very interesting thread. Wanted to follow up on one post I found there:
"In some circumstances, none. However, you can think of Expression as a subset of Volume. If the Volume is set at 100%, then Expression is identical. If the Volume is set lower, then Expression will allow you to use much smaller increments of volume change. I tend to use Expression for er, expression and Volume for relative volume to other instruments (mixing).
Of course, there are some products by other companies where volume doesn't work. In those situations you have to use Expression for both.
DG"
Technically, couldn't you also reverse the two (other than for products where volume doesn't work)? I.e., if you set expression at, say, 64, doesn't cc 7 become a fine volume control? I realize this seems pedantic - but I've often found that small points like this end up being useful in unexpected ways.
PL