That irrestible coquette known as "Naughty Marietta" turned 70 years old this week, but keep it quiet because the old girl looks and sounds as young as ever. Victor Herbert's 1910 operetta is on stage through Sunday at the Baird Auditorium, and it is a hit.

This tale of a runaway countess who roams the wilds of Louisiana Vocalizing a haunting tune was a spicy prelude to the Broadway musical, combining techniques of opera with the best elements of the vaudeville and Yiddish theater traditions. The results were as charming as they were influential. It also had unforgettable songs like "Ah, Sweet Mystery of Life" and "I'm Falling in Love With Someone," as well as a very funny book. The Smithsonian production is only semi-staged and with a piano. But I will not voice my semi-annual prayer against semi-stagings here, because the cast makes up for everything, and all the flavor and excitement of the work have been captured alive.

Judith Blazer is magnificent in the title role. She is a crystal-clear lyric soprano with a small but gutsy voice. Her Marietta is sexy. Her comic timing is the best, her naughtiness always tongue in cheek. It was a pity that only the finale of the "Italian Street Song" was encored, because here was a star the audience would have gladly listened to all night.

In the comic role of Simon O'Hara, and Irish American with a Jewish accent, Steve Liebman stole every scene he visited. Leslie Harrington was an attractive but tight tenor Captain Dick, and Wayne Turnage was dashing in the double role of Etienne and the pirate. As Adah the quadroon mistress, Elvira Green showed off a hefty technicolor mezzo, even if little stage presence. The whole business was directed with speed by James R. Morris, who also conducted.

The Catholic University a cappella choir had nothing to envy other opera choruses heard here, and if the Casquette girls looked a tad embarrassed, they sounded glorious.