The singing voice of Jean Stapleton has been heard by more people than any other singer this side of Kiri Te Kanawa -- but "Those Were the Days," the theme song of "All in the Family," hardly gave her talent its full scope. How much can you do with a song whose most poignant line is "Gee, our old LaSalle ran great," particularly when you are required to sing it in an ear-piercing falsetto?

She has considerably more to do in the world premiere production of Lee Hoiby's one-act, one-character opera "The Italian Lesson," and she is doing it with distinction for the Baltimore Opera Company, with seven more performances scheduled through Feb. 3 at the Peabody Conservatory's Friedberg Concert Hall, an acoustically excellent small auditorium.

Because it is a premiere and because its entire cast is one famous performer, "The Italian Lesson" is the highlight of the current Baltimore production, titled "American Portraits." But it is only one-third of the program, which is made up of three one-act operas, each lasting about half an hour. And the other two pieces are worth a trip to Baltimore, for those whose minds are not totally closed to contemporary opera.

For connoisseurs of American theater, "The Italian Lesson" has been something special for more than half a century. It is a monologue (the best of about three dozen) invented by actress-author Ruth Draper portraying a hectic morning in the life of a wealthy Manhattan matron. Adapting it for opera is an enormous challenge -- one with which Hoiby wrestled for 10 years -- but he has managed it superbly.

Athough Stapleton is alone on the stage throughout, she is usually talking to someone. Her gestures and dialogue populate the scene with as many as seven or eight characters at a time including her children, manicurist, cook, maid, secretary and the Italian teacher ("Signorina"), who is supposed to guide her through Dante's "Inferno." They never get past the first three lines, which she sings several times at intervals throughout the opera in a solemnly portentous tone.

The carefully calculated interruptions and her comments on Dante ("It's divine; one realizes how it has come down through the ages") and on life in general gradually unfold a complex portrait -- hilarious and pathetic at the same time -- of a shrewd but stupid, utterly self-centered woman who has woven an elaborate web of busyness to cover the essential emptiness of her personality and her life. Character (or the lack of it) is shown in the way she orders a dinner for eight that evening, and in her dialogue (monologue, actually) with her secretary about what to do with her tickets for the symphony and how to get some men for her box at the opera: "Do you know anybody who likes music? Well, everyone says they do, but I never really believe them."

It is shown in her attempts to discipline her children, in her gushing over a new puppy, which she names "Dante," in her plans for the afternoon (a contract bridge lesson at 3, a philosophy lesson at 4), and in the way she orders a new book called "Our Inner Life" -- "I don't know who wrote it, but I have to discuss it at the book club on Friday, and I want to run through it before then." Her milieu is also treated incisively, largely through phone calls that keep interrupting the Italian lesson: from friends who want to gossip about the latest scandals; from her husband, who wants his golf clubs left at the railroad station; from her lover -- when she sends everyone out of the room on various errands, and suddenly her tone of voice changes completely.

It is a richly textured theatrical tour de force, requiring a brilliant actress, and Hoiby has wisely avoided piling overambitious musical demands on top of the role's theatrical requirements. He has composed the music in a sort of arioso recitative that can and does shift easily either into spoken words or brief intervals of lyric ecstasy. Above all, he has taken great pains to preserve the clarity of the text. His music paces and energizes the words, comments on them, gives them emotional accents and never gets in their way. He has written the vocal part in a sort of all-purpose women's range, generally comfortable for either a soprano or a mezzo. In a few measures, he has written high or low alternative lines.

Stapleton handles the musical requirements satisfactorily (she shows what we might call a good Broadway voice), and her acting is magnificent. Plans are being discussed for a performance later this season at the Kennedy Center's Terrace Theater, where it should work well.

Thomas Pasatieri's "La Divina" is a hilarious skit about the final performance of a world-famous coloratura soprano. It has a cast of four, including a magnificently temperamental soprano who requires more than 30 acrobatic notes to say "Thank you. Ah, thank you." It also has a fine caricature of a young conductor and two strong supporting roles for the prima donna's maid and manager. It is a slight thing, but perfect of its kind and it receives a near-ideal performance.

Hugo Weisgall's "The Stronger," based on a short play by August Strindberg, is a psychological study of the superficial friendship and profound rivalry between two women, one of whom sings nonstop while the other registers her feelings without uttering a word. The question, which of the two is the stronger, depends on the performers in any given production. When the opera is produced in Scandinavia (as happens fairly often; it is Weisgall's most-performed opera), the silent role is usually taken by a leading actress such as Ingrid Bergman or Viveca Lindfors. It is a fascinating little work, with constantly changing emotions, a superbly expressive vocal line and colorful comments from a seven-piece orchestra.

The impact of the Baltimore performance on opening night was somewhat diminished; the words are crucial, and the diction of soprano Patricia Craig (a Metropolitan Opera regular) lost clarity in her upper register. This should not have happened in the Friedberg hall; it was not a problem in "La Divina" or "The Italian Lesson."

"La Divina" is expertly performed by Carol Gutknecht, Martha Jane Howe, George Massey and James Katchko. Henry Mollicone conducts well in all three segments, and Gerald Freedman's stage direction is generally capable, though a few sections needed further polishing on opening night.