Monteverdi retained emotional and political attachments to the Mantuan court and wrote for it, or undertook to write, large amounts of stage music including at least four operas. The ballet "Tirsi e Clori" survives through its inclusion in the seventh book, but the rest of the Mantuan dramatic music is lost. Many of the missing manuscripts may have disappeared in the wars that overcame Mantua in 1630. The most significant aspect of their loss, according to Carter, is the extent to which they might have provided musical links between Monteverdi's early Mantuan operas and those he wrote in Venice after 1638: "Without these links ... it is hard to a produce a coherent account of his development as a composer for the stage". Likewise, Janet Beat regrets that the 30-year gap hampers the study of how opera orchestration developed during those critical early years.