What explains why the Philadelphia Orchestra’s BeethovenNOW concert, with two full symphonies webcast from an empty Verizon Hall on March 12, is up to 771,000 YouTube views? Or why the Rotterdam Philharmonic’s abbreviated Beethoven 9th video — with each instrumentalist playing separately from home, titled From Us to You, is closing in on 2 million views since its March 20 posting? – Philadelphia Inquirer