Francesca Buchalski leaned heavily on plastic foam, floral wire and other craft-store staples to assemble evening wear for her first orchestra concert last month at Philadelphia’s Mann Center for the Performing Arts.

The 15-year-old Allentown, N.J., sophomore is part of a new generation of symphony patron that is invigorating the bottom-line performance of concert halls across the U.S. She dressed as Link, the elfin warrior from “The Legend of Zelda,” a series of Nintendo Co. videogames that inspired the night’s program....