Theater Review : Is This the Sandra She Wants to Be? : Bernhard calls ‘Excuses for Bad Behavior’ a work in progress. So far, her sincerity and singing are less effective than confrontation.

Half an hour after the scheduled curtain time, Sandra Bernhard’s Thursday night show at the La Jolla Playhouse’s Mandell Weiss Theatre hadn’t yet started when a techie came out among the guitars and drum set to check the mikes. The audience was in the mood to take out their lighters, when the house lights finally dimmed. Was this a rock concert, a parody of a concert, an evening of stand-up with music or a piece of performance art? Answer: It’s whatever Bernhard says it is.

“Excuses for Bad Behavior, Part I”--and when did Bernhard ever need any excuses?--is a glimpse into where this idiosyncratic and, to many, bafflingly confrontational, performer is heading. Having its “world premiere” in La Jolla through tonight, the show will begin touring in September in conjunction with the release of her album.

Onstage, and with her trademark menacing tone, Bernhard warned any critics present that this show is a work in progress and should be treated as such. Her anxiety is clearly a case of projection: When she gets going, no one is a more vicious or funnier critic.

Looking fabulously toned in a silver sheath mini dress (or is it a slip?) and with her hair in a curly bob, she demolished a Vanity Fair writer simply by reading aloud from the Sylvester Stallone cover story, which contained, among other adoringly lascivious descriptions, “his little rosebud of a mouth” and “the hair-raising brevity of his cotton shorts.” Bernhard raises contempt to a high art.

“Sunset Boulevard” also took a bruising. In Bernhard’s hilariously uncharitable imitation of Glenn Close, whom she calls “scary,” the star sang, “Sunset Boulevard/Nutty, stinkin’, (expletive) boulevard . . . .” In the next breath, though, Bernhard performed a ballad from another Andrew Lloyd Webber hit, “Jesus Christ Superstar,” with a fair amount of feeling. She and her five-piece band, complete with backup singer, played both original and well-known songs.

In recent interviews Bernhard has spoken of a need to open up emotionally in her art even as she becomes saner and more content in her personal life. Disappointingly, the evening was devoted more to music than stand-up. She obviously takes her singing seriously but still seems inhibited somehow; her persona uses stylish hostility to keep us far away from her true feelings. Like any gifted comedian, she’s a better truth teller in her scathing mode than in her more sincere one.

Bernhard is brilliant at forced intimacy. In Martin Scorsese’s film “King of Comedy,” Bernhard sang, “You’re gonna love me/Like nobody’s loved me/Come rain or shine” to a celebrity hostage played by Jerry Lewis, who was bound to a chair under a hill of thick tape. Here, threat hangs in the air when she tells the audience, “I feel sad and I want to share with you.”

It’s hard to know how to feel, though, when she mourns a list of friends who have died of AIDS in the same soft, insinuating voice that she has used to skewer show-biz insincerity. The audience sometimes seemed unsure which Sandra to respond to.

Easier to recognize, and funnier, is the nice Jewish girl from Michigan gone raunchy, reading aloud from X-rated phone sex ads. She also sings “50 Ways to Leave Your Lover” with female names (“Just get off the phone, Joan”) and struts, in her encore, like Aero-smith’s Steven Tyler, only in a red Lycra micro-mini.

At the moment, “Bad Behavior,” which is scheduled to come to Los Angeles in the fall, is a snapshot of an unclassifiable performer in transition.

Is that fair enough for a work in progress?

* “Excuses for Bad Behavior, Part I” plays tonight at the La Jolla Playhouse, Mandell Weiss Theatre, 7:30 p.m., $34, (619) 550-1070.