Aha! Thanks Thomas - that does answer a big part my question! From what you're saying the loudness requirements for streaming services are still typically well above those for broadcasters (8 to 10db louder!)
I don't (and haven't) delivered songs to spotify or other streaming services - so there's the rub!
What I'm getting from all of this is that there is probably nothing going on with this plug-in that I am likely to need for my own work.
Ironically, given Raymond's post (Hi Raymond!) I bought Wavelab 9 about a year back in the big sale, just to cover off a situation where I might have to deliver audio for CD or similar - (very unlikely for me nowadays) - as Wavelab natively has some pretty neat mastering tools (MasterRig).
I think I'll stick with what I have for now. The difference between me using the tools that I already have for mastering/limiting and using the PSP plug-in are probably small enough that the defining feature of my use of either would be my lack of specific mastering expertise/monitoring set-up. I'm sure for the mastering pro's quoted on the product review there's far more tangible benefits.
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Guy - in quick reply to your post - I can see how there's a temptation to simply mix to peak levels just like in the old days, because then everything works just like we always used to - and for certain programming, yes, that does make sense
Cheers all!
Chris