Physical Graffiti is, perhaps, Led Zeppelin's most visceral offering. The expansive double album mixes fresh recordings with unreleased cuts held over from previous projects, but all 15 tracks hit home with swaggering confidence. The opening cut, "Custard Pie," is all about vicious, guttural guitar riffs meeting some of Robert Plant's most blues-inspired lyrics. The 11-minute "In My Time of Dying" is a heady, epic workout, while the unstoppable "Kashmir" is sparked by one of the most taut and menacing intros in all of rock.