Metropolitan Opera soprano Teresa Zylis-Gara has been asked to sing at the mass for Solidarity in St. Matthew's Cathedral and is trying to clear her schedule to be here when it begins at noon tomorrow. Another soprano -- mezzo Renata Babak, who defected from the Bolshoi Opera during a tour of Italy -- will sing in honor of Solidarity tomorrow night at American University. Joining her in the concert, which is sponsored by the Sakharov International Committee and the National Fine Arts Foundation, will be Ukrainian-born bassbaritone Andrij Dobriansky of the Metropolitan Opera and pianists Alan Mandel and Jerome Reed.

Other musicians participating in Solidarity Day observances will range from Frank Sinatra to the chamber ensemble of the D.C. Youth Orchestra. Sinatra will sing in Polish on the massive telethon Sunday, produced by the International Communication Agency and titled "Let Poland Be Poland." The Youth Orchestra will play the American and Polish national anthems and Copland's "Fanfare for the Common Man" at tomorrow's rally sponsored by the AFL-CIO.

Among the Polish artists in exile who will be featured in the telethon are Jan Sawka, whose exhibit of paintings closes today at the International Monetary Fund; Adam Makowicz, who was acclaimed by Downbeat magazine as the best jazz pianist in Europe, and Nobel Prizewinning poet Czeslaw Milosz.