Mozart not only depicted Alexander the Great in his opera Il Re Pastore,
but took this text from Sant'Angiolo-Morbilli's libretto to Paisiello's
La disfatta di Dario (The Defeat of Darius), which takes as its storyline
Alexander's conquest of Persia and the death of its king, Darius. The aria
was written for Gottfied von Jacquin, a noted bass of the time.
In this aria, Darius leaves his daughter, and sings of his terror and unhappiness
at having to do so. The orchestral introduction, largely dominated by
clarinets, is mournful, and the frequent pauses give it an air of
hesitation, of someone trying to force himself to leave.
The first part of the aria is slow-paced, as he sings "As I leave you, o
daughter, my heart trembles in my breast. Ah, what a bitter parting! I
feel, in my grief, madness and terror. I am leaving. You weep?" In this
section, Darius' grief is mostly expressed by lines that move downward
in pitch, but in the next section, as he longs for a moment more, and
becomes more agitated, the pace quickens significantly, and his lines
build up to high notes.