Read the interview with Markus Schmidt, one of the makers of the Calf Plugins, at LibreMusicProduction.
Warning: some strong language is used – tho in this case it even seems appropriate; you will understand after reading.
His band from that time, Jammin’Inc* is also a good tip. You may download and use all that stuff, as it’s under a CC license. As are the Calf Plugins and everything else Markus is using now (except that Debian and other software is of course GPL).