7:30 pm: Music

Victor Vener and the California Philharmonic begin a new season of “Festival on the Green” summer concerts in the lush setting of the L.A. County Arboretum with “All American,” a program of Gershwin, Copland, Gould and Sousa. Arboretum doors open at 5:30 p.m. for pre-concert dining. Order in advance from participating restaurants or bring your own picnic dinner. Artists will display their works in an open-air art festival at the concert.

* Festival on the Green “All American” concert, L.A. County Arboretum, 310 N. Baldwin Ave., Arcadia. $10-$45. (626) 844-6600.

10 am: Museums

The Model J Duesenberg, considered the apex of American automotive craftsmanship, performance and engineering, is the subject of “It’s a Duesy,” a new exhibition at the Petersen Automotive Museum. Unveiled on the brink of the Great Depression, Duesenbergs became the cars of choice for movie moguls and screen idols. Models once belonging to William “Hopalong Cassidy” Boyd, Bill “Bojangles” Robinson and Tyrone Power, along with more than 20 other 1930s Duesenbergs, will be on display.

* “It’s a Duesy,” Petersen Automotive Museum, 6060 Wilshire Blvd., Los Angeles. Through January. Tuesdays-Sundays, 10 a.m.-6 p.m. Adults, $7; seniors and students with ID, $5; children ages 5-12, $3. (323) 930-CARS.

7 pm: Brazilian Music

The Brazilian Summer Festival, always one of the season’s liveliest parties, takes a traditional turn this year with the Sambacoustic Choro Band, a five-piece ensemble that explores Brazil’s samabas of the ‘30s and ‘40s; Josias & Sambrasil, with cavaquinho player Josias Dos Santos, and the colorful Ballet Folclorico Do Brasil. Looking for carnival-in-Rio dancing and costumes? The Tropidanza Dance Ensemble will shake its feathers in hot Brazilian chorus-line style.

* Brazilian Summer Festival ‘98, John Anson Ford Amphitheatre, 2580 Cahuenga Blvd. East, Hollywood. $25; children under 12, $7. (323) 461-3673.

10 am: Family

The Ronald Reagan Presidential Library’s “Old-Fashioned Family Fourth of July Celebration” celebrates America’s birthday with a replica of a Revolutionary War soldier encampment, including period crafts, arms and clothing, George Washington look-alikes, storytelling, carnival games, patriotic music, pie-eating contests and more.

* “Old-Fashioned Family Fourth of July Celebration,” 10 a.m.-4 p.m. Ronald Reagan Presidential Library and Museum, 40 Presidential Drive, Simi Valley. Free admission. (800) 410-8354.

8 pm: Theater

For a comic spin on the Fourth of July, there’s “American Twistory,” a cabaret musical revue of songs and sketches spoofing American history, directed by David Galligan, with music and lyrics by Kevin Kaufman and John Everest.

* “American Twistory,” Cinegrill, Hollywood Roosevelt Hotel, 7000 Hollywood Blvd., Hollywood. Saturday, 8 p.m. Regular schedule: Mondays, 8 p.m. Ends July 27. $10. (213) 466-7000.

Noon: Pop Music

The reunited X headlines the fourth annual Hootenanny Festival, a modest, folksy reminder of why rock ‘n’ roll has been worth preserving. The show at Oak Canyon Ranch brings together rockers old and young, the originals together with the tradition-honoring branches that have sprung from the roots, to celebrate rock’s heritage. The lineup also includes Social Distortion, Reverend Horton Heat, Cramps, Lee Rocker, Supersuckers and others.

* Hootenanny ‘98, Oak Canyon Ranch, 5305 Santiago Canyon Road, Irvine. Also Sunday at noon. $32.50. (909) 715-2252.

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Freebie: “Salute to All Americans” concert, Beverly Hills Civic Center Plaza, Rexford Drive, 3 p.m. (310) 550-4796.