By Guy D.Garcia

Her trademarks used to be hot pants and hard rock, but these days Linda Ronstadt, 37, is more comfortable with organza and lush orchestras. "I've always been eclectic in my tastes," says the Arizona-born singer. Last week she would have done any 40s prom proud at the World's Fair in New Orleans as she kicked off a nationwide concert tour that will feature a full orchestra conducted by mainstream Maestro Nelson Riddle, 63. Ronstadt's fondness for retro chic is getting to be longstanding. In 1980 she reached back to Gilbert & Sullivan when she did The Pirates of Penzance, first on stage, later in a movie version. Then in 1983 she made What's New, a hit album of '30s and '40s classics. After the current eight-week tour, Ronstadt and Riddle will begin recording a second collection of old standards. And this fall Ronstadt will return to the Public Theater in New York City to sing Mimi in an English version of Puccini's La Boheme. What next, Gregorian chant for soprano?

His resonant portrayal of a washed-out country singer in Tender Mercies won him an Oscar, but for Robert Duvall, 53, the sweetest reward was the praise for his singing performance that came from real country-and-western stars like Johnny Cash and Willie Nelson. If it worked on the silver screen, why not try for a gold record?

Last week Duvall was in Nashville cutting an album of country music with the assistance of such chums as June Carter Cash and Waylon Jennings. "People do that around here--help each other out," says the California-born actor. Singing runs in his blood like trout in a country stream. "My younger brother sings tenor with the Milwaukee opera company, and another brother sings tenor in Washington, D.C.," he says. "I've loved country music since I was 13."

If a shaggy-dog story is a tale without any real ending, then this is a shaggy-dog story. The dog in question is Nemo, and he belongs to former Pittsburgh Pirates Star Willie Stargell, 43, and his family. When Stargell heard that a dog-food company was running a "Search for the Great American Dog," he figured that had to be Nemo, his 2 1/2 year-old part German shepherd. The celebrated base hitter even submitted an essay of the required 50 words or less on why Nemo should be named Most Valuable Pooch. Wrote Stargell, obviously from the heart: "He's one in a million." The winner gets $25,000. Will it be Nemo, prompting all the noncelebrity contestants to cry foul? Finalists will be announced in October, and then the public gets to vote. Making the All-Star team could not have been more nerve-racking.

The musical was last seen in 1927, when its satire of inane economics, bumbling bureaucracy and pointless war proved a bit strong for audiences. A reworked, watered-down Strike Up the Band eventually made it to Broadway, but the original version of the George Gershwin-George S. Kaufman collaboration disappeared. More than a half-century passes. Enter Marjorie Samoff and Eric Salzman, looking for the right play to open their newly formed American Music Theater Festival. They pieced Band together with the help of the late Ira Gershwin and Anne Kaufman Schneider, the playwright's daughter. It opened last week in Philadel phia with a cast led by Saturday Night Live Veteran Bill Irwin, 34, a practiced stage clown. "It's a pretty garbled satire," admits Irwin, "but it has a wonderful thrust." The Inquirer critic liked Irwin and the rest of the cast, but the play, he thought, did not survive the reconstructive surgery.

-- By Guy D.Garcia

On the Record

Maureen Reagan, 43, G.O.P. consultant, on why she is critical of her father's tendency to refer to all women as "ladies": "Women is something we are, lady is something we earn."

Norman Cousins, 69, former editor of the Saturday Review: "The great threat to the health of our people is not cancer or terminal illness but the foreign policies of governments."

Fernando Bujones, 29, leading dancer with the American Ballet Theater, on an artist's need to overcome the trepidation of trying a new role: "We are paid for our fears."