Joseph Mollicone's one-act opera, "The Face on the Barroom Floor," was designed to be performed in a barroom, the Teller House in Central City, Colo., where it is revived every year. It manages to preserve the saloon atmosphere in its first Washington production, even though it is being staged in a Presbyterian church by Opera Southwest.

A tall, mustachioed bartender with just the right kind of rich baritone voice (Barry Hahn) presides genially, telling a chilling story of violent death, pouring drinks and pulling a gun from under the bar at the crucial moments. The tables are festooned with semi-derelict drinkers, sitting silently in Levis and checkered shirts, equally believable parts of a scene today, or a century ago when a barmaid was accidentally killed while two men were struggling over a gun.

After the bartender has told the story to two tourists, a modern parallel to the 19th-century tragedy is reenacted, and soprano Denise Freeland is killed twice, in two roles, within half an hour. It does seem a bit severe, even for a singer who has unclear diction and an edgy sound in her upper register, perhaps intensified by the acoustics of the Westminster United Presbyterian Church.

In the third singing role of this mini-opera, tenor Ray Hornblower has fine tone and an excellent sense of word values; a final evaluation of his acting ability must await his appearance in something with a more substantial plot. The "orchestra" is a flute and cello, plus a piano played in fine honky-tonk style by composer Mollicone.

Interactions of past and present, illusion and reality, and the strange workings of fate also are the subject of the second opera of this Mollicone double feature: "Emperor Norton," musically and dramatically a much more substantial work than "Barroom." It is set in modern San Francisco, where a playwright, mezzo-soprano Joan Morton, is preparing a script on Emperor Norton, an eccentric street person who shocked and amused the city in the 1850s.

Helping her with the project are a young actor and actress (tenor Paul McIlvaine and soprano Debora Madsen), whose reading of her script is interrupted by a mysterious, outlandishly dressed intruder (baritone Lewis Freeman, who evidently is the ghost of Norton). He insists they have the story wrong, restages key scenes from Norton's viewpoint and eloquently conveys the idea that eccentrics are people like the rest of us.

"Norton" is more recent than "Barroom" and seems to show substantial growth in Mollicone's mastery of the difficult form of one-act opera. Its emotions, ranging from near-slapstick comedy to pathos, are good raw material for his eclectic, easily accessible style, and he gets outstanding performances from Morton and Freeman and adequate work from McIlvaine and Madsen, who show both potential and a need for more seasoning.

Such seasoning, as well as this kind of imaginative programming, is one reason for the existence of small companies like Opera Southwest. The production, which will be repeated tonight and tomorrow night, lacks the polish of large companies with high-priced tickets, but it fills a vital role in our operatic ecology.