Anyone who starts trying to use modeling of some sort can blow this one, because they don't add an equivalent amount of compression to match the "tube sound."
Your EARS are compressors. AIR is a compressor, the soggier the air the more compression. I'd say, in order:
1) Speakers are the biggest compressor out there, as well as drastic tone controls. Why doesn't anything above 5K come out in real life? Because your speaker ATE IT.
2) Tubes are the next biggest culprits, what people call the "sweet spot" is exactly where a tube amp is compressing the most.
3) Ears. Your ears (and brain) automatically redesign the music as it's passing by.
4) Strings, hands, picks... pluck a string hard. Now pluck it even harder. Does it get any louder? No. It's reached it's limit, and past that all it does is compress. Absolutely EVERYTHING in a music transmission system has a limit, past which it can't go. What would you call that?
A) - No. You don't need any extra, because you've got a truckload of compression working already!
