Frequencies compression (as peak one) allows you boost the overall volume of your track which in turns increases its loudness <=> RMS.
Of course you must take care of peaks but meters (and ears) are your friends.

http://jamin.sourceforge.net/en/loudness.html

regards
-r

Thank you for remind me on this article Ron. It was one of the first that I discovered when I started using Linux Audio. But hey, it took me a whole year to figure out how all the different audio apps work here in Linux and which ones are useful to me, so I lost sight of that one, I must admit. I will take my time to study it a bit closer.