Janice Hall, who ususally sings such roles as Gilda in "Rigoletto" or Lucia di Lammermoor, made her debut last night in a new role: Rosina in "The Barber of Seville." Through the years, many sopranos have seen no contradiction in a career that included all those roles, but for Hall last night it was a new experience. She sang Rosina, not in the coloratura style that has been familiar for more than a century, but in the mezzo-soprano range of Rossini's original manuscript.

It was a one-time appearance for Hall, substituting in this performance only for Zehava Gal, who is singing the Washington Opera's other 10 performances of "Barber" this season. Hall, whose chief reason for being in Washington at the moment is a soprano role in "Wiener Blut," which opens next week, proved to be equally at home as a mezzo.

Her lower register was firm and rich in tone, exquisitely precise both in pitch and in diction, and to these virtues she added the agility of a fine coloratura in the upper range. Her acting was as fine as her singing, and for this single appearance, she fit in well with the rest of the company, who have been performing it for more than a week.

A week into the opera's run, the orchestra seems to be coming to terms with Rossini's music more gracefully than it did on opening night. Not quite halfway through its stay at the Terrace Theater, the Washington Opera's "Barber of Seville" seems to be shaping up as a fine production -- memorable not only for its use of Rossini's seldom-heard original score, but also for the fine dramatic and musical direction, and the generally high quality of the singing.