Opera International presents only one production per year, always in August, always in the Lisner Auditorium and always with a power and elegance that belies the company's small size and modest budget. This year's "Tosca," given its first performance last night, fulfilled all the expectation built up by the company's past achievements. There will be a repeat performance tomorrow at 4 p.m.

"Tosca," like most operas that have become classics, is a tribute to the perennial interest in sex and violence, enhanced by the energizing powers of great music. English critic Ernest Newman once called it a "shabby little shocker," a questionable description but the sort of thing one expects from a dyed-in-the-wool Wagnerian.

Shocking it certainly is, with its offstage sounds of a man being tortured, its onstage firing squad and its intricate pattern of betrayals that result in violent deaths for all three principals. But the villains are no more shabby than the gods, giants, dwarfs and dimwitted heroes who populate the "Ring" Cycle; great operas seldom build their plots on nice people.

"Little?" Maybe compared with Wagner, but it is Puccini's closest approach to the epic style of Verdi. We might invert Newman and call "Tosca" a giant, sumptuous shocker. That's what it is in this production, with its striking sets emphasizing its epic dimensions.

In the title role, soprano Hai-bo Bai captures the full complexity of Tosca--proud, insecure, funny in her moments of jealousy in Act 1, vulnerable enough to make her plea of helplessness, "Vissi d'arte" ("I lived for art"), totally believable but tough enough to kill the lecherous police chief Scarpia with a table knife when he attempts to sexually assault her. Bass-baritone Sun Yu, vocally resonant and smoothly hypocritical, is convincingly sinister as Scarpia, as is tenor Giancarlo Bacigalupo in the role of his henchman Spoletta.

There were a few insignificant rough notes in tenor Drew Alan Slatton's "Recondita armonia" in Act 1, but he acted the part with unusual skill and his "E lucevan le stelle" in Act 3 had emotional and musical depth. Good work was done in supporting roles by Jason Stearns (Angelotti), Yu-Hsi Bai (Sacristan) and boy soprano Zachary Eden Bernhard as the offstage shepherd boy whose folk song opens Act 3.

Conductor Edward Roberts and director Muriel Von Villas paid strict and rewarding attention to the finest points in Puccini's explicit, detailed and often ignored musical and theatrical instructions.