AC/DC may possess a sound unlike any other, but they didn't start out that way. Long before they were riding the highway to hell, the Aussies were cutting their teeth on import records from the other side of the globe. Brothers Malcolm and Angus Young had no shortage of six-string heroes: Jeff Beck's spare but blistering blues-rock riffs. Cream's updates to delta blues. Hendrix's searing, crunchy shredding. And for a taste of both Bon Scott's and Brian Johnson's vocal inspirations, look no further than Zeppelin singer Robert Plant's impassioned cries or Alex Harvey's primal, glammy wails.