Back home, I started my investigation and found that this particular station had broadcasted the opera Olimpie (or Olympie) composed by a certain Gaspare Spontini. The piece was based on a play by Voltaire (well, well, …) and was performed for the first time on 22 December 1819 by the Opera de Paris. The opera has been translated in Italian and in German and was renamed, Olympia.
It is obvious that the story is pure imaginative for there is no known daughter of Alexander and no historical Olympie.
The story is set after the death of Alexander when his successors are fighting for control of his empire. The two main characters in the play are Cassandre, the son of Antipater, and Antigonus, one of Alexander’s generals. The fiction starts with Stateira, daughter of King Darius and Alexander’s widow who in reality was killed upon Roxane’s orders. In the opera, she survives incognito as a priestess of Diana in Ephesos.
The opera implies that both Cassandre and Antigonus were involved in the murder of Alexander in Babylon. After fighting each other, they finally agree to make peace but then they both fall in love with the same girl, Aménais, who is nobody else than Stateira’s daughter by Alexander, Olympie. Aménais/Olympie is in love with Cassandre but Stateira accuses him of murdering Alexander. Aménais/Olympie pleads for Cassandre who saved her life, while Stateira turns to Antigonus for revenge. The armies of both men clash and on his deathbed, Antigonus confesses that he is responsible for Alexander’s death. The happy end is that Olympie and Cassandre get married.
A soundtrack of the opera can be found on this Youtube link but no live images exist because Spontini’s opera success was short-lived due to his competition with Gioachino Rossini.