In an attempt to suggest a clue to the answer to my own question, .....and it may sound like I'm talking out of the side of my mouth here as I fully admit that I'm no sound engineer and the highly scientific and technical aspects of why this stuff works the way it does is as foreign to me as Chinese algebra. I had the pleasure once of visiting and speaking with George Wright of
Wright Sound. When I asked him why tubes sound distinctive from SS, the explanation he offered had something to do with exactly how the two reproduced a signal. If you run a signal through a SS amp to an ocilliscope the graph will read as a stair-step hard straight line, rising and falling off like a cliff. Run the same signal through a tube amp and it reads as a curve, rising and falling off more gently. This reminds me of the difference between digital and analog reproduction where the digital represention of the curve of analog becomes a very fine stairstep that represents that curve. The other distinction that I've heard made is that tubes impart certain orders of harmonic distortion that our ears/minds equate more directly with music (or perhaps just as 'pleasing'). To further the description of what I like about tube+horn reproduction of sound that may relate to this: there is something about the way it lets the music just linger in the air and fade off that is very appealing and natural to my ears. SS tends to sound more abrupt and does not have the same sense of "lingering". OK, so enough of my butchering away at scientific (mis)information. Someone who is far more versed in this stuff needs to step in here and set me straight!
Marco