With his latest release, Jonas Kaufmann ventures deep into the little-charted territory of Austro-Hungarian operetta. “Magische Töne” (“Magical Sounds”) is indeed a potpourri of Belle Époque mystique: playful, mischievous, and bittersweet. Its 22 tracks comprise lyrical evergreens like the “Wolgalied” (“Es steht ein Soldat am Wolgastrand”), alongside the rather obscure “Julia” by Paul Abraham, as well as Fred Raymond’s {…}