It's been a journey of more than 30 years for Alice Cooper from national nightmare to national park. But that is where the shock rocker will find himself performing tonight when he takes the Filene Center stage at Wolf Trap, touring in support of his latest studio recording "Dirty Diamonds."

When the original Alice Cooper band emerged from the glam and art rock scenes of the early 1970s, critics were aghast at the macabre spectacle of hangings and beheadings that were part of its live performances. Even those who eschewed the band's concerts found offense in recordings of such songs as "Dead Babies" and "I Love The Dead."

But a funny thing happened to frontman Vincent Damon Furnier (who shrewdly adopted the band's name as his own when the original line-up split) on his way to the Filene Center. People began to figure out what Cooper's good friend Groucho Marx knew all along: It was all just show business, a sort of dark vaudeville.

These days Cooper seems to relish his role as one of America's most famous Jekyll and Hyde acts. Offstage he is a businessman, philanthropist, doting father, avid golfer, Christian and supporter of conservative politicians. But the onstage "Alice" (Cooper speaks of the "character" he plays on stage only in the third person) is still something that emerged from the murkiest cesspool of the id.

Cooper likes to depict his performances today as modern versions of medieval morality plays, which become a catharsis for his audiences' negative emotions and sinful impulses. And the concerts still provide Cooper with his own nightly exorcism: The shows' over-the-top theatrics culminate in the execution of that evil alter ego that Furnier adopted so long ago.

While the band Alice Cooper invented shock rock at the dawn of the '70s, another arena rock act, Cheap Trick, crafted a new genre at the decade's close. Cheap Trick's mix of strong melodies, hard-edged guitar and speedy rhythms defined what would become power pop. Everyone from 1980s pop-metallers and punk-rockers to 1990s alternative rock groups would find something to love about the band. Cheap Trick also brings its unique sound to the Wolf Trap tonight.

With a decidedly eccentric fashion sense and uncommonly good ears for tasty hooks, the group -- singer/guitarist Robin Zander, guitarist Rick Nielsen, bassist Tom Petersson and drummer Bun E. Carlos -- has scored several hits during its career including "Surrender," "I Want You To Want Me," "Dream Police" and "The Flame."

-- C. WOODROW IRVIN

The Filene Center, 1551 Trap Rd., Vienna. Tickets are $25, $42 and $75. To purchase tickets call 877-965-3872 or visit www.wolftrap.org.

Alice Cooper, shown during July's Montreux Jazz Festival in Switzerland, performs tonight at Wolf Trap.