Quite easy: Imagine, you are Hans Werner Henze, standing in front of the orchestra, ready to start playing. Then U say: "Stop! I want every single instrument or section (such as the HO-4) play its loudest note allone!" Result: If the VI-16_mV play the loudest possible G3 at - 13 db, the VA-10_mV reach a peak of - 16 db, the single horn reaches - 20 db and so on. If U transfer this situation to your setup: U have everything set to start composing (all volumes, reverbs, pans, etc.). Even if U plan to automate your volume faders afterwards, it is still a setup, U consider to be a good mix to start with, no matter what velocity the single instruments might play later. So as soon as you are confident with your mix, stop it at any time of your work to check, what maximum peak every single instrument is able to play. Then all people like me would have something very good to start with, because I would just have to adjust the volume levels. In my situation, not knowing the relative levels, I might set the HO-4 volume fader too loud and later on balance that in a false way by letting them play mf instead of ff. Do you see my point?
A-HA - We are not talking about the same matter.
I see now what you mean, but that is what we call absolute dynamic (Felix sez: "play its loudest note"). But there is a difference between absolute and relative dynamic.