Wow, "sometimes subtly" and "sneak them in"? How do you do that with such a distinctive and identifiable sound?!! This is a serious question as well as an expression of surprise. I think of myself as pretty musically aware, yet I can't imagine any major 7th sounding subtle. Take it away and you have gesso where there was once a fine painting. IMHO of course.
CH. (back from sick-land)