Fresh after his Oscar nomination, violin virtuoso Joshua Bell threw an event at his Manhattan penthouse that was so enthralling, some had trouble leaving. Guests including Julianna Margulies — who dashed from the set of “The Good Wife” — Mark and Renee Rockefeller, Ralph Lauren, Gayle King, Christine and Stephen Schwarzman, Carol Alt, and Tommy and Dee Hilfiger were treated to a performance by Bell to honor nonprofit Education Through Music. Bell — the rock star of classical music — is nominated for Best Original Song for “Before My Time,” which he performs with Scarlett Johansson in “Chasing Ice.” The buzz at the party was that he may perform at next month’s Oscars. Others there included Debbie Bancroft, Boykin Curry, Kyle MacLachlan and Desiree Gruber. Unable to make it were Glenn Close and Meryl Streep, who both succumbed to the flu. The only off- note in the lyrical evening was when the elevator in Bell’s Flatiron building jammed, forcing some guests to stay put for another cocktail.