There are at least two juicy specimens in the traditional operatic repertoire that most people would consider candidates for the title of Best Beginner's Opera. The qualifications? Start with a gorgeous, accessible score, full of tuneful arias that take up permanent lodging in the memory bank. And all that ear candy has to be harnessed in service to a high-stakes drama full of passion, betrayal, desperation, etc., with turns of plot relatively free of those unlikely developments and last-minute reversals that set the eyeballs to rolling in some other operas.

Georges Bizet's melody-rich "Carmen" is the front-runner for a lot of folks, what with its steamy seduction scene, outbursts of jealous rage and that dagger-to-the-rib cage denouement. Even though the music is undeniably memorable, it can get a little bit draggy, with four acts stretching out over 3½ hours.

Less of a challenge for the uninitiated is my personal pick, Giacomo Puccini's masterpiece, "Tosca." It has a fast-moving, credible plot propelled by political intrigue, romance, sadistic cruelty, courage under torture, vengeance and treachery, and it clocks in at two hours and 40 minutes, tops. Best of all, the music is unforgettable, from the ominous, downward-stabbing chords that open it through some of the most glorious, heart-rending arias ever written ("Vissi d' arte" for the soprano, "Recondita armonia" and "E lucevan le stelle" for the tenor).

If you wrap that all up in a package that includes great staging and top talent in the starring roles, then you've got all the ingredients that could conceivably make a convert out of a newbie operagoer.

Hope is aflutter, then, for San Francisco Opera's production of "Tosca," which will feature two world-famous sopranos alternating in the title role throughout the 12-performance run, which opens Thursday in War Memorial Opera House. Our first Floria Tosca is the gifted Romanian Angela Gheorghiu, who will sing opposite tenor Massimo Giordano as Mario Cavaradossi for six performances, with baritone Roberto Frontali as the thuggish sexual predator Scarpia.

Also cast as Tosca is acclaimed soprano and longtime S.F. Opera favorite Patricia Racette, who begins her run Friday night, with up-and-coming tenor Brian Jagde, a third-year Adler Fellow, as her Cavaradossi and baritone Mark Delavan -- also an S.F. Opera stalwart -- as Scarpia. S.F. Opera music director Nicola Luisotti conducts the performances of the Thierry Bosquet-designed production, which is directed by Jose Maria Condemi.

Details: Through Dec. 2 at 301 Van Ness Ave., San Francisco. Tickets, $22-$340, are at 415-864-3330 and www.sfopera.com.

ORNAMENTAL SONG: Boston-based sopranos Kathryn Mueller and Kristin Watson, known as the duo Les Sirènes, make their West Coast debut this weekend on the San Francisco Early Music Society's concert lineup, with a program titled "Virtuosi Italiani: The Florid Style of Monteverdi and Handel." Accompanied by Cora Swenson on cello and Michael Sponseller on harpsichord, they will perform arias and duets written in the highly embellished Baroque style that Claudio Monteverdi made popular in the 1600s and Georg Friedrich Handel brought to polished perfection a century later. They appear first at 8 p.m. Friday at Palo Alto's First Lutheran Church and move to Berkeley's St. John's Presbyterian Church for Saturday's 7:30 p.m. concert, winding up Sunday at 4 p.m. at St. Mark's Lutheran Church in San Francisco. Tickets, $30-$35, may be purchased at the door or through www.sfems.org.

ANOTHER PLUCKY DUO: João Luiz and Douglas Lora met 15 years ago as teenage guitar students in São Paulo and have been performing worldwide as the Brasil Guitar Duo ever since. They concentrate on expanding the repertoire for two guitars, with Lora composing and Luiz arranging classical and Brazilian works for the combined instruments. Hear some of the results at 8 p.m. Saturday when they perform in the Green Room of the War Memorial Performing Arts Center at 401 Van Ness Ave., in San Francisco. Tickets, $34, are available at 415-242-4500 or www.omniconcerts.com.

IF YOU'VE GOT IT, FLAUT IT: She's only 16, but Pleasanton's Foothill High School student Annie Wu last year became the youngest performer in the 33-year history of the National Flute Association to win its solo competition. She piled up major cred in Europe this summer, playing in Vienna, Berlin and other venues. She will be guest soloist for the Diablo Symphony's 4 p.m. Sunday concert in the Lesher Center for the Arts in Walnut Creek, playing the Ibert Flute Concerto. Matilda Hofman, Diablo's new conductor, will also lead the orchestra in works by Mozart, Verdi, Brahms, Barber and Chabrier. Tickets, $10-$25, are available at 925-943-7469 or www.lesherartscenter.org.

Contact Sue Gilmore at sgilmore@bayareanewsgroup.com.