Thanks for the info and correction. My ignorance is showing - looks like I've misunderstood some of the details of the technology and terminology.
With this corrected understanding, I guess my main question is simply: Is my assumption that there are no high-quality orchestral samples available (and usable, in a practical sense) for Linux systems incorrect? From your response it sounds like the answer might be yes (i.e., good news - high-quality samples are available).
I find it hard to get precise information on this with google (at least without spending a lot of time, which I'm not willing to do right now). It looks like the Vienna Symphonic Library (VSL) samples exist in Kontakt format - bad news, apparently, since I accept your implication that Kontakt samples cannot be used easily on Linux. It looks like VSL might also be available in DSL, which perhaps is good news - you seem to imply that DSL samples can be played on Linux. (I don't think I had heard of DSL before you mentioned it here.) Of course, there are other high-quality sample collections besides VSL. Do you know if any of these are playable on Linux, in a practical sense and, if so, where should I look? (If it matters, I use rosegarden to compose music, and I'm looking for good-sounding samples so that I can improvise [as a basis for composition] and allow the sound to inspire me [which tends to lead to good/creative musical ideas], instead of what often happens - a somewhat unpleasant and uninspiring result due to mediocre sounds.)
My question, I suppose, is pretty broad and perhaps hard to answer with the needed detail, but if you think what I'm looking for exists and can provide me with some pointers, hints, key-words, or such to help me find what I'm looking for, I'd appreciate it. (In case it matters - Windows is not an option for me - I'm allergic to it; and OSX is probably not an option either.)