For two weeks this summer, amid the wail of guitars and the thrum of stadium crowds, Amber Tamblyn lived out one of the great rocker-chick fantasies: She danced onstage with Neil Young. "I got to rock out," says Tamblyn, who joined a troupe performing on tour with the Canadian singer, a family friend. "At the very end of the show, I'd get up on someone's shoulders and hold up a big peace sign."

As the star of CBS's new hit drama Joan of Arcadia, Tamblyn, 20, has traded rock and roll for the rock of ages. She plays Joan Girardi, a confused teen on a spiritual quest who encounters God as a lunch lady, a TV newscaster and a cute guy, among other guises. "The other day we were sitting in the hair and makeup room giggling as we listened to the South Park Christmas album, and the next moment we're doing a scene and she's making me cry," says Mary Steenburgen, who plays her mom. "Amber is this wonderful combination of being an incredibly smart, old soul and being silly and goofy."

Add aspiring singer-author to the list. Tamblyn recently recorded a song inspired by her show called "God and Me" with Young playing backup and has published two books of Beat-influenced poetry, Of the Dawn and Plenty of Ships. (Sample lines: "She said/ Aren't the stars lovely?/ I thought/ Yeah, but what good are they a million miles away?") If it seems she was born a few decades too late, she says simply, "I don't see the importance of doing it the way everyone else does."

Her parents never pressured her to conform. Russ Tamblyn, 68, who played the Jets' gang leader in 1961's West Side Story, and his wife, Bonnie, 56, a teacher, gave their only child ample freedom when she was growing up in Santa Monica—not to mention a circle of very cool family friends. Hearing stories about the likes of Young (Russ choreographed and directed his old pal's summer tour) and Dennis Hopper fed Tamblyn's artistic hunger. After watching her portray Pippi Longstocking in a school play at age 9, Russ's agent asked to take Amber out on casting calls. "She blew everyone away," says Russ. "But I wanted her to grow up first. I thought auditions would burn her out."

Dad gave his blessing anyway, and when at age 11 she landed the role of Emily Bowen Quartermaine on General Hospital (which she played for seven years), the adjustment was tough. "I couldn't play or go to birthday parties anymore," Tamblyn says. "It was hard to not have relations with kids my age."

That changed in her teen years, when she used her freedom to occasionally stay out at raves until 6 a.m. before reporting to the General Hospital set. "I told my parents everything that went on in my life," she says. Though she avoided the club drugs, Tamblyn still harbored a wild streak: At 16, she got some risqué piercings. "Because I was on a soap opera, I could never dye my hair," she explains. "Finally I thought, 'I'll rebel secretly.' My dad was so upset, he wouldn't talk to me for days."

Tamblyn hasn't gotten the silent treatment much since, by her own admission, she's mellowed into a true-blue nerd. "I don't shop for clothes at all. I'd rather go to a bookstore," says the actress, who lives with her boyfriend of more than three years, music producer Travis Burkheimer, 29. "Travis is a geek. Give me a computer guy with a fat belly any day. I love brainy guys." Naturally, Dad approves: "I told Amber as long as she's happy and upbeat, whatever she does is okay."

Not knowing what God and Arcadia's writers have planned for Joan is keeping Tamblyn content these days. As for her own personal mission, she sees her future self as a college grad and a loving mom. "There aren't enough good men in the world, so I want to get married and raise some really good boys," she says, adding she'll also be fiscally responsible. "My mom is adamant that I know how to do my taxes by the time I'm 21." Then again, all this independence can get a little lonely. "I miss my mom's cooking," says Tamblyn. "But she's only two blocks away, so I can say, 'Mommy, can I come home for dinner?' "

ANNE MARIE CRUZ
Lorenzo Benet and Sean Daly in Los Angeles