The 18th century experienced a mass migration of musicians from Italy seeking better fortunes in nations to the north. Geminiani, Cervetto, and Cirri went to London, Boccherini to Madrid, and Vivaldi aimed for Dresden though never arrived, having died en route in Vienna. These Italian instrumentalist/composers and others are the focus of “Out of Italy,” an exploration of sonatas and duos for two cellos and continuo by eminent baroque cellist Phoebe Carrai and her protege Beiliang Zhu, some of them quite rare.