Jem Aswad Senior Music EditorA new lead singer is just about the most dramatic change a band can make — even if a main songwriter or instrumentalist leaves, the voice is usually the clearest link to what came before. Although George Clarke, cofounder and lead vocalist of long-running San Francisco avant-metal act Deafheaven, hasn’t gone anywhere, he’s changed up his style so dramatically for the band’s fifth studio album that it actually sounds like they have a different singer.