What has more than 8,000 feet, thrives on heat and humidity, and loves Beethoven's 9th? Why, it's the audience attending Yannick Nézet-Séguin's first gig at the Mann Center in Philadelphia's Fairmont Park! More than 4,000 attendees were recorded at the SRO event June 24, though it's hard to keep track of seated patrons when there is wine, beer, and Rita's Ice to purchase in the open-air lobby. Events at the Mann…