Mumford and Sons have spent their almost 20-year career puzzling out a big question: to stomp or not to stomp? The banjo-banging modern folk they came up with on their 2009 breakthrough Sigh No More and its 2012 follow-up Babel didn’t just make the U.K. band unlikely stars, it changed the pop music mainstream . Their rustic aesthetic heralded an acoustic music boom that included acts like Ed Sheeran, Noah Kahan, and Zach Bryan, and their sound crept into the rhythms of pop. Like any band with a