THE PENNSYLVANIA BALLET will continue its season, rescued from the fear of folding by a vigorous fund-raising campaign that has netted the company $1.2 million - a big step on the road toward the $2.5 million needed by July 31. When the company took its problem to the people, they responded with a flurry of $25 checks, which ballet officials hope will stimulate corporate contributions. Dancers and staff are again working for pay, after having donated their services for two weeks.

- SILVER ANNIVERSARY TIME rolled around this year for three stalwarts of the Metropolitan Opera, each in his/her 25th season. They are soprano Mirella Freni, tenor Alfredo Kraus, and bass Nicolai Ghiaurov. Still all in remarkably good voice, the three were honored with a gala on March 24 at the Met, assisted by Placido Domingo, Frederica von Stade, and Samuel Ramey.- THE ROYAL DANISH BALLET will visit the United States next year, to mark the 500th anniversary of the discovery of America. They will perform in Los Angeles and Washington, D.C., said artistic director Frank Anderson.

- JAZZ WILL BECOME LEGIT at New York's Lincoln Center, with Rob Gibson as head of the newly created Department of Jazz, projecting three programs a week by summer. Nathan Leventhal, president of Lincoln Center, expects the new entity to have a $1 million budget by the mid-'90s. Wynton Marsalis is the center's artistic director for classical jazz.

- ANTONIN DVORAK slept there, and that's reason enough to grant the Czech composer's New York residence landmark status. In the row house in New York's Greenwich Village where Dvorak lived 1892-95, he composed his famed "New World" Symphony. The Beth Israel Medical Center had opposed the move, saying it wanted to tear down the house and build a hospice for AIDS patients.

- STEINWAY PIANOS, for a century and a half the touchstone among American instruments, has struck a deal with Kawai Musical Instruments Manufacturing Co. to design and manufacture upright and grand pianos for Steinway with mass production techniques, rather than the painstaking hand-customed instruments of the past.

The Kawai/Steinways may not carry the Steinway name, though they will be manufactured according to Steinway specifications. Reasons for the change are falling demand for pianos at the top of the price scale, and the public's desire for small, cheaper grands for beginners.

Kawai thus gains a prestige image, but some fear that the Steinway name may be cheapened. Kawai sold about $245 million worth of pianos last year, with a price range from $3,000 to $59,000. Steinways in Japan start at about $26,000 and sell for as much as $100,000.

- EARLY HANDWRITING of Johann Sebastian Bach has been discovered in a musical manuscript housed at the Carnegie Library in Pittsburgh. The three-leaf manuscript is a copy of a prelude and fugue by the German composer Dietrich Buxtehude, probably copied by Bach and his older brother Johann Christoph about 1695. It shows that Bach had knowledge of Buxtehude's fugues 10 years before scholars had previously supposed. The manuscript will be retained at Carnegie Library, where it will be exhibited after it has been de-acidified. It may be worth as much as $250,000.