Summer seasons have long been a touchy issue with orchestras – they tend to lose money, are hard to sell, and frequently require an investment in a special summer venue that may or may not pan out. A few years back, the Minnesota Orchestra’s Sommerfest was a textbook example of a failing summer season, playing to half-empty halls and searching for an identity in a city packed full of summer activities. But in the last three years, ticket sales have jumped 30%, a 24-hour marathon kickoff day has become one of the signature events of the year, and this summer, half of the orchestra’s Sommerfest concerts sold 95% of capacity or better.