Amid the symphonic blockbusters regularly staged in the large museums of New York City, the special exhibitions mounted at the Frick Collection in three quiet, elegant rooms on the lower level of the museum offer visitors a welcome dose of chamber music. Striking in this regard was the summertime exhibition of works by the eighteenth-century Genevan artist Jean-Étienne Liotard, whose spare but penetrating portraits, character studies, and still lifes filled the Frick’s small space with...