The New Explorers (PBS, 8-9 p.m.): Whale songs -- wavering, sirenlike, (interminable?) -- aren't exactly whistleable, but they have their fans, and scientists are among them. On ''The Sounds of Discovery,'' this edition of the noted science-adventure series, host Bill Kurtis takes viewers on some technologically advanced efforts to record the whale calls.
In one, a marine biologist becomes the first scientist to put a special tag on a sperm whale. He hopes it will send a signal to a satellite so scientists can track the elusive creature's migration route.
In another section, aboard the nuclear submarine USS Montpelier, the Navy collaborates in searching for the ''acoustic signature'' of whales with a network of underwater devices originally designed to track enemy submarines.
And in an unplanned moment, the production's camera crew records an unusual whale-human interaction when they come upon a group of pseudorcas (false killer whales).
A&E Stage (A&E, 9-10 p.m.): Mozart's ''Requiem'' is moving enough by itself, but this performance brings an added resonance to the great work: the setting. The concert takes place in Sarajevo, on the site of the Sarajevo Bibliotheque, once the Sarajevo City Hall, which was destroyed during the conflict.
Filmed last year, the concert boasts some of the world's best-known musicians, including Zubin Mehta, who conducts the Philharmonic Orchestra of Sarajevo, and singers Jose Carreras, Ruggero Raimondi, Ildiko Komlosi, and Cecilia Gasdia.
During the program, old shots are screened showing the splendors of the Sarajevo Bibliotheque, a medieval structure that once housed cultural and historical treasures. The show ends with an appeal for donations to the children and needy of Sarajevo.
Please check local listings for these programs.