judgements on virtousity are best made by players of a particular system, very few other[ to my knowledge] than A Anderson, G Cutty, lea Nicholson AND myself have attempted RAGTIME PEICES or duet style [on the English], with out double tracking.
then we must consider skill at double tracking, Lea Nicholson comes into the picture again, on both his lps [but particularly the second one]
but is technical virtuosity of paramount importance, well when combined with musicality, yes, but not as in an end in itself.
   musicality is a subjective opinion, personally I respect every player who has put in hours of practice.