What would Guns N' Roses have been like with an injection of estrogen? Gina Gershon brought that alternate reality to life for a lucky few when she rocked out last week with former GN'R members at the Sundance Film Festival.

The actress took the stage (click to see photos) January 21 at Cisero's in Park City, Utah, at a party for her upcoming movie "Prey for Rock & Roll," in which she plays Jacki, the frontwoman of ne'er-do-well all-girl rock band Clam Dandy. She hooked up with the former Guns after running into drummer Matt Sorum at the Whiskey Bar in Los Angeles a week before the festival.

"I just kinda pimped myself out for the gig," Sorum said, "and pimped my friends out too."

With little time to prep, Slash, Duff McKagan and Sorum — who played guitar, bass and drums for GN'R, respectively — threw together a set, including two songs from the movie. Gershon, despite having sung on Broadway in "Cabaret" as well as in her upcoming film, was a little apprehensive.

"I've played live with people before," the actress said, "but in different sorts of things. And in the movie I'm in character. I was a little intimidated. They're listening, and I'm like, 'Oh, God.' But there was no time for intimidation. We just had an hour for rehearsal. I just stressed until I knew what I was doing."

Gershon found ways to ease her nerves, such as cribbing her lyrics on the inside of her forearms. "When it looked like she was fainting from passion," Slash said, holding his arm up to demonstrate, "she was just reading her lyrics."

"Every now and then, it was like, 'Yeaaaaah, you keep singing and a'walking,' " she sang, holding her arm to her face. "It's a neat little trick."

Not that the crowd — which included Gershon's "Prey" co-star Drea de Matteo, singer Ben Lee and actress Rachael Leigh Cook — could tell she wasn't fully ready. Gershon and the boys, who recently reunited for a still-untitled new project, blazed through a set that included covers of Nancy Sinatra's "These Boots Are Made for Walkin' " and the Stooges' "I Wanna Be Your Dog," during which McKagan sang with Gershon.

With her unabashedly sexual stage presence — Gershon felt herself up and flipped her shagged hair as she held tight to the mic stand — the actress seemed every part the rock star that her "Prey" character dreams of becoming.

"She just came in for one night, but she came in with the attitude that we wish a thousand singers could come in with," Slash said.

"I just had fun," Gershon said with a smile, "so much more fun than my day job. It's instant gratification. When we were doing the movie and I was in the recording studio, I just kept thinking, 'What have I been doing all these years?' Musicians are so great."

Despite her gushing, don't expect Gershon to sign up for the vacant singer spot in the former Guns N' Roses members' new band. They're still holding auditions, Slash said, "looking for that elusive singer guy."

Also a contender is another singer who joined them at the Sundance show, Waylon Jennings' son, Shooter, who fronts the L.A. rock band Stargunn. Jennings belted out lead vocals on Bad Company's "Feel Like Makin' Love," the Rolling Stones' "Sympathy for the Devil," the Damned's "New Rose" and such GN'R songs as "It's So Easy" and "Paradise City." Jennings played a similar covers set with the band in June after a show by McKagan's band Loaded.

"We started getting about 150 CDs a week [after MTV's last report in November]," Slash said (see "Former Guns N' Roses Members Form Band, Don't Rule Out Courtney Love As Singer"). "After Christmas it dwindled a little bit, but we've been getting CDs from all over the place."

In MTV's November poll, viewers and readers overwhelmingly picked Chris Cornell over suggestions like Courtney Love, Marilyn Manson, Kelly Osbourne and Sheryl Crow.

"If I had a choice, if I could actually go, 'Let's go get him and steal him out of his band,' there is one guy I do want who's also taken," Slash hinted, "but until it's set in stone it's not done."

For more sights and stories from concerts around the country, check out MTV News Tour Reports.

— Jennifer Vineyard, with additional reporting by Nick ZanoNick Zano