ROSSINI: “ERMIONE.” Cecilia Gasdia, Margarita Zimmermann, Ernesto Palacio, Chris Merritt, Simone Alaimo; Prague Philharmonic Choir; Monte Carlo Philharmonic Orchestra conducted by Claudio Scimone. Erato ECD-75336 (two compact discs). Hailed as a major discovery when exhumed for the Pesaro Festival a few years ago, this 1819 tragedy seems a trifle resistible on its first commercial recording. Tottola’s libretto, based on Racine’s “Andromaque,” and Rossini’s formal, “through-composed” complexity require singers of authority, fearless attack and stylistic acumen. Merritt and Palacio exercise tenorial perogatives with uncomfortable results.