The magic festival moments people talk about years later are the ones where nature and performance conspire together -- and during Robert Plant's performance at Mountain Jam last night (June 5), when a wall of fog rolled in, that moment was upon us.

It's not just because it was visually stunning, which it obviously was, but Plant's performance already had a kind of veil over it. Plant does modified versions of Zeppelin songs with his band, the Sensational Space Shifters, where heavy passages, like the classic headbanging chorus on "Babe I'm Gonna Leave You," are replaced by acoustic guitar, and rippers like "Rock and Roll" take on a slow, vaguely electronic sheen. Above it all, always, is Plant's voice, essentially untarnished by the years. It was astounding how good it sounded.

A version of "Whole Lotta Love," one of the hallmarks of Plant's stage show in recent years, slowed to a standard Delta blues before bursting into the classic Page riff, and then slowed, and then burst forth again. By then, the fog had enveloped the stage, the lights forming thick columns that shot all the way up the mountain.

One song that broke through the fog was Plant's take on Bukka White's 1940 "Fixin' to Die Blues." Plant could not have ever been in finer form than he was tonight, and if Friday's performances -- from Grace Potter's vocal-cord-shredding blues to Joan Osborne, of Trigger Hippy, and her soft, southern-rock soul singing -- are any indication, his style of sweating out the blues on stage is very much alive.

Still, we couldn't help but read "Fixin' to Die Blues" as a meditation on mortality, if simultaneously a celebration of influence. "Don't mind dying," sang Plant. "But I hate to leave my children crying."