I was recently reminded once more of how I am out of touch with contemporary popular culture when I stumbled across an assessment of Marc-André Hamelin’s rendition of a Liszt Hungarian Rhapsody as “retarded.” My first reaction was dismay, because I have always admired Mr. Hamelin’s dexterity, expressiveness, and virtuosity, and I could not imagine what would lead the correspondent to label his playing—even of Liszt—in such a negative fashion. Of course, I then realized that this is another one of those cases in which the uses to which a …