As detailed in the previous discussion on the topic, there is certainly a danger in applying modern ideas on virtuosity to earlier music, and especially in transferring philosophical priorities on the subject. However, the phenomenon of virtuosity itself deserves closer consideration. In common language, being a virtuoso is basically synonymous with being a highly skilled musician. It would certainly be difficult to find fault with that! However, historical usage gives the origin of the term in a sort of connoisseur dilettante or basically someone who does things in a superficial manner. The idea of superficial virtuosity is certainly not new, and inasmuch as it is clearly derived from the term virtue, seems to have arisen as much as a reference to culling the fluff of virtue than from any sincere connection.
I might say that virtuosity is the foam on the sea of music, that it makes a fine addition to a seascape, but that it is valueless or even disagreeable if bottled on its own. The idea is not widely held, at least not today. Modern criticism and evaluation of composition places opportunities for performer virtuosity as a positive or even necessary criterion for excellence. Many nineteenth & twentieth century classical works have virtuoso display as their primary end. Although virtuosity as a phenomenon can be traced clearly to the Baroque, the Romantic exaltation of it goes on to be linked partly with ideas of transcendence, and so to something more than gratuitous display. Breaking the bounds of physical performance was intended partly as a wink toward other modes of thought, and so as an evocation of something beyond ordinary experience.
While virtuosity is one important means by which to open new ways to articulate ideas, from Ockeghem's bass voice to advances in violin technique which allowed a range of sonority, one must keep in mind clearly what those ideas are. While simply proceeding with an idea in the hope that it might work is sensible to a point, the danger of ultimately pursuing novelty for its own sake lurks nearby. Novelty, another philosophical idea established in the Baroque period, at least in language, has little real relevance, and is ultimately corrosive of an artform, if not of society as a whole. It bears repeating that ideas on the value of novelty, and consequently virtuosity in its vulgar sense, are ultimately philosophical, and perhaps the dominant popular aesthetic philosophy of our times as exemplified in the "been there, done that" phrase. The virtue of humility is frequently lacking, even disparaged, and so I might suggest that it is fundamentally humility which separates useful virtuosity from useless virtuosity.
In other words, a virtuoso must repeatedly ponder his own relevance. Having the fastest fingers is nothing in and of itself, just as merely being able to perform an unusual act does not immediately place it as a beacon to other modes of thought & experience. By his nature, the virtuoso stands out both against human norms and against a musical fabric. The latter demands a soloistic conception of music, perhaps best exemplified by the concerto format. The former conjures a broader image of performer as such, not just as someone to create music to be heard, but as someone to be seen and someone to serve as an example of excellence, in short someone to be on a stage. There is consequently a fine line between someone whose superior physical skills are perceived as an extension of the human condition and as something to which others can aspire, and someone whose physical gifts are deployed so as to emphasize distance from ordinary humanity and from the audience. Again, the deciding factor in this case is usually humility.
The implication is then that the virtuoso cannot signify transcendence without involving the audience in a more active way, and that indeed it is partly kinesthetic identification which allows the stage of performance to reach beyond simply making sounds. In this sense, stretching physical limits can lead to an expansion of audience awareness, whereas flouting them cannot. The former emphasizes continuity while the latter emphasizes distance. This is precisely the way in which one can evaluate virtuosity as a tool of virtue, especially as habits of behavior reinforce themselves. The basic idea can be given an analogy in composition as well, where a density of notes can derive by extension of a real lexical organization or from something more "inhuman." The division between the two is not clear-cut, however, as the former could end up as nothing more than chattering nonsense whereas the latter could yield a new & worthwhile form of expression. In many ways, this arbitrary division can be mediated by the physical act of performance itself, perhaps with the aid of a virtuoso to demonstrate the naturalness of something which might hitherto have been poorly articulated.
An ability to find a true & inclusive means for expressing musical ideas which had languished is the surest sign of virtuosity in its lofty form, especially as physical ability combines with the mental acuity to perceive the correct balance of issues in a passage. In this area, there is no space for simply being able to play notes faster than anyone else, as tempo and its effects on signification are rather more subtle than that. What a virtuoso can do at his best is to let a passage make sense, especially when it did not receive the necessary clarity in the past. This is an area which points less toward personal quirks of stardom than it does toward improvement of technique in aggregate. Other than aspects of dexterity-based speed and articulation, virtuosos may be known for their sonorities, especially vocal sonorities. An acquaintance with world music clearly demonstrates that sonority preferences do not transfer across different types of music, and so this kind of virtuosity is of the more perception-dependent variety.
Philosophical ideas surrounding the "virtuoso" today are frequently those related directly to the culture of consumption. Although these ideas certainly mediate the way in which music functions today, even old music, they do not necessarily reflect its circumstances. In order to unravel many of the most affecting aspects of medieval music, we must shed some of our preconceptions about the nature of individual performers and performance. This goes both for sonorities and their relationship to articulation as well as the relative place of individual display. What it involves ultimately is the recognition of other aesthetic philosophies, not just for their historical curiosity, but for their actual usefulness. Likewise, the virtuoso can be put to good use in the articulation and clarification of musical ideas, especially if given the proper feedback.