Singers of Imperial Russia (Pearl, distributed by Koch International): four volumes, each with three well-filled compact discs of opera stars you never heard of from such locales as pre-Revolutionary St. Petersburg, Moscow, and Warsaw.... All this seems, on the face of it, rather a lot of a dubious thing. Well, one must make allowance for the sound. Surface noise lies on some tracks like a trace of dust, on others like dark, thick layers of cracking varnish. But how thrilling the voices are that call out across the chasm of the years! What vibrant personalities! Not to mention how much unfamiliar, haunting music they sing. And occasional salvos of enthusiasm from studio listeners make it feel as if one were back in the room when the artists sang straight into the horn. Here is a treasure trove, indeed.