Across Europe, the music directors are getting younger and younger. Not so in the U.S., with the notable exception of the Los Angeles Philharmonic’s recent appointment of 26-year-old Gustavo Dudamel, who may just change the landscape. “If the fiery Venezuelan galvanizes attention, as seems likely, the ripple effect will spread as far inland as Chicago and New York, dispelling the paralyzing caution and opening the box to a new breed.”