Old news is good news from The Opera Company of Boston. Sarah Caldwell et al. are busy shoveling mothballs from the sets and costumes of Rossini's comic opera, ''The Barber of Seville.''
If there's anyone out there who has just come out of a cave and still thinks opera is an expensive substitute for counting sheep, I suggest you wake up and get to the box office for this one.
In 1974, only the voices of Beverly Sills and Donald Gramm were able to drown out the laughter and howls of this production. From the entrance of Figaro out of the orchestra pit to the rescue of Rosina locked in a bird cage, the production soared.
This time around, Ruth Welting, who had everyone eating out of her mechanical hand as the windup doll in the ''Tales of Hoffmann'' excerpt at the 25th anniversary gala in February, leads what promises to be a strong cast.
This is one of the most entertaining evenings I've spent at the opera. You have two opportunities to see it - tomorrow night at 8 p.m. and Sunday at 3. - J. E. Young