FESTIVAL ’90 : Pianist Looks for Clean Start : Music: Avant-garde performer Sandra Tsing Loh composes a symphonic score for drivers at a Santa Monica carwash.

Classically trained pianist Sandra Tsing Loh wants to be taken as a serious musician even though her Open Festival event Saturday, “Music at the Bonus Carwash,” may do little to dispel her reputation for staging amusing avant-garde musical performances.

The former Caltech physics major and USC English literature graduate student whose ’87 Fringe Festival concert over the Harbor Freeway became the butt of Johnny Carson’s “Tonight Show” monologue has composed a five-minute symphonic work that’s said to combine eerie “Twilight Zone” sounds with Gershwinlike passages to accompany the wash, rinse and dry processes.

“Some people will think it’s funny, brilliant or silly,” Loh said. “What’s important is that people respond, show up and it becomes a topic of conversation.”

Loh, 28, expects 40 participants between 6 and 8 p.m. to pay $15 to sit in their cars while listening to her audiocassette. Ten people have made reservations; 40 will cover her $300 costs for the event and the carwash on Lincoln Boulevard in Santa Monica cannot accommodate more cars in the two-hour period.

After 1988’s “Self-Promotion” concert when she showered her audience with 1,000 $1 bills and last year’s “Night of the Grunion” performance with the Topanga Symphony in Malibu--complete with spawning fish--Loh feels it’s time to strive for critical recognition. Her first solo album, “Pianovision,” produced by jazz musician Buell Neidlinger, is set for a fall release.

“I’ve always wanted to create a big image that people will remember for the rest of their lives, a surrealistic dream people will walk away from and say, ‘I can’t believe somebody did this,’ ” Loh said. “But with the album, my music is appraised on its own merits, not because there’s money flying in the air or fish in the sand. It’ll have to stand on its own.”

Loh’s comedic musical monologue on American movie musicals was well received at Theatre/Theater in July and she has performed at local clubs.

And Loh is working on next year’s project: “Sigalert,” a participatory traffic jam on an abandoned freeway that climaxes with a staged five-car collision.