Hi Beagle,
What I mean by this is that the sonic character of the preamp and mic combination will be revealed throughout the widest range of dynamics.
The singer will taunt the input with quiet passages as well as thunderously loud passages.
Most opera singers don't use mic technique... they just sing!
A lot of signal chains have a sweet spot... the great signal chains have a really wide sweet spot.
This is the type of scenario where I, personally, feel that I can easily hear a difference between good grade stuff, which I use almost every day, and the really really good stuff which I only pull out on special occasions.
I pulled my John Hardy M1 out of the rack last night to take in to town because I think the performers are prepared to make use what it can offer.
all the best,
mike