Classical music begins with blood and guts. The first violins were strung with sheep intestines, while early timpanis bore heads made from goatskin. The conservatory-bound spend years blistering, bruising, and contorting themselves, sometimes to the point of permanent damage. On the Francis Bacon-inspired cover of her new album, Noémi Büchi lies splayed out and bloodied on a plastic sheet, a sight that evokes both a cocoon and a Dexter kill room. Büchi, a Swiss-French sound artist and classically trained pianist — the late Romantic period and early modernist periods are her province — titled her new album after the Latin “exuviae.” To Virgil, these were the spoils stripped from an enemy combatant’s body; to a modern-day entomologist, they’re the husks…