Um- some of that seems a bit complicated. I _write_ soft clipping plugins (AU plugs) so I'll explain. Actually, one of my best is definitive soft clipping.
Suppose you have a sound. It goes up in loudness until bam! it hits the 0 point, can't go any louder, and the top of the wave is neatly chopped off. That's hard clipping. Actually, a lot of mastering engineers use hard clipping, not soft, simply because it does less to all samples below that point. It's the loudest-seeming sort of clipping. It's also the ugliest, brightest, and most likely to cause problems down the line with further processing.
Suppose you said, let's start clipping BEFORE we get to zero. Well, if you just chopped the sound off earlier, it would still be hard- but what if we sort of had the sound slow down, so you'd have to put a lot more volume in to get to zero? Up to a point it would be full volume and as you pushed past that point things would START to distort, but you'd still be getting a waveform out. You can even set it up so that the closer you get to zero, the harder you'd have to push the level to get there. This is soft clipping.
The idea is, you have to put increasingly high level to get up to zero db, but it's not time-based at all, so it's not a compression or limiting- it's purely distortion on each individual sample, and with soft clipping the distortion starts BEFORE you reach top volume, sometimes a lot before. Here are some examples: http://www.airwindows.com/m/Density.mp3
This is my Density soft clipping plug. (first dry, then effect.) The distortion in this one is always on- the term 'knee' is used to define 'where the effect switches over from clean sound to altering the sound'. Density is such soft clipping that the entire range of loudness from silence to 0dbFS is the knee. Nothing out there is softer clipping, technically. Does that make it ideal for getting loudness, in, say, mastering? Not really, because there isn't enough of a 'clean zone', it will make everything sound fuzzy and distorted in a weird tubey way. http://www.airwindows.com/m/Drive.mp3
This is my Drive soft clipping plug (first dry, then effect.) This one, the distortion works in an unusual way, where if you have a waveform (like the top of a wave) and you use Drive to clip it, in an editor it appears that you sort of slid the top of the wave up without changing its shape. This is a considerably less soft clipping, but it's still softer than DAW buss clipping. For me this one works great on drums- I also have a version of it in my Peak Limiter as a post-limiting extra loudness boost, and after that, simple digital clippers to catch overs- soft to hard, always, for clean loudness.
The more soft the clipping is, the more it will dirty the sound up in an appealing way. Instead of getting nasty bright clipping, you will get more of a soft warm grunge- but it will color more of the sound, not just the very biggest peaks. It's a trade-off. The thing to remember (that I wasn't seeing people mention) is that soft clipping means MORE distortion affecting more of the music, not that you get to go over 0 dbFS in the end. It means, simply, that you start distorting sooner so you don't have to get it all at once in a nasty bright splat.
Did that help?
Those plugs can be got, here: http://store.kagi.com/cgi-bin/store....D=6FEGJ_LIVE&&
Plus, a more subdued version of the Density ultra-soft clipping can be had FREE in the Channel plugin, here: http://www.airwindows.com/f/Channel.dmg
(same soft clipping, but not as much of it, combined with some tone shaping)