The former governor of Pennsylvania may have been correct when he characterized America as "a nation of wusses." But if that's so, Led Zeppelin fans are surely the exception to the rule.

On Wednesday night, the Philadelphia region was transformed into a fearsome landscape that looked for all the world like the frozen "land of the ice and snow" that Robert Plant once ululated about in "Immigrant Song."

But that was not one of the Led Zep tunes the 62-year-old, gray-goateed golden god sang that night to a packed house of hardy souls at the Tower Theater, during an often-breathtaking 100-minute set with his six-piece knockout ensemble Band of Joy.

For the record, Plant and Band of Joy - which shines a spotlight on the luminous talents of guitarist-bandleader Buddy Miller, multi-instrumentalist Darrell Scott, and singer Patty Griffin - did reworked versions of five Zep songs: "Tangerine," "Houses of the Holy," "Gallows Pole," "Ramble On," and, yes, "Rock and Roll."

Plant is the still-restless soul who walked away from the biggest uncashed check in the business in 2007 when he chose to make music with country fiddler Alison Krauss rather than follow a one-off Led Zep reunion in London with a full-fledged tour.

For him, the songs by his thunderous classic-rock band are not exactly beside the point, but rather just one piece in a large musical whole that encompasses British Isle folk and American country, blues, gospel, and rock-and-roll.

Plant correctly believes that he can best explore that range of roots music with the group of Nashville cats who make up Band of Joy, gathered together by producer Miller on the 2010 album of that name that is the rougher, louder equal of 2007's Grammy-grabbing Krauss collaboration, Raising Sand.

At the Tower, that was borne out repeatedly, sometimes on songs where the charismatic front man took the lead, and sometimes when he let others step to the fore. "Monkey," a cover from the American indie band Low, was a murky, mesmerizing duet with Griffin. Scott moved front and center for "A Satisfied Mind," a country standard delivered with robust, churchy harmony singing that turned the Tower into a sanctified space.

Equally impressive was the Plant-led "Satan Your Kingdom Must Come Down" and "Move Up," which Griffin delivered with an earthy soul that stood in contrast to the crystalline elegance that characterizes Krauss' pairings with Plant.

In what by all rights could be a comfortable senescence, the spirit clearly still moves within Plant. "Ah, music, why do you do this to us?" he asked, unbidden, then jokingly answered, "I guess it's better than chocolate."

At one point, Plant was moved to shimmy his hips and shout out to South Street and Bobby Rydell. And for further proof that the aging rock deity actually knew where he was, he made reference to another Philadelphia institution, free-jazz explorer Sun Ra, after a revised rendering of "In the Mood," from Plant's 1983 solo album The Principle of Moments.