Gluck had no scruples about grinding several grists from the same sack and drawing from his old works to help out his new ones. So the parasitical aria attributed to Bertoni was written by Gluck in the first place in 1764 for a soprano. He wove this into his opera _Aristo_ in 1769. This is also true of the trio, _Tendre Amour_, which precedes the finale in the last act. A serious-minded analyst might be tempted to admire the profound psychology of the author in mingling doleful accents with expressions of joy, but he would have his labor for his pains. The trio was taken from the opera _Elena e Paride_, where Gluck expressed strongly wrought up emotions. Doret did not keep these two passages and one can"t blame him. On the other hand, he retained, by making it an entr"acte, the _Ballet des Furies_. This was taken from a ballet, _Don Giovanni o il convitato de pietra_, which was performed at Vienna in 1761. This passage was used as the accompaniment to Don Juan"s descent into Hell, surrounded by his band of demons.