The master of the duet at age 14

Mitridate, re di Ponto (Mithridates, King of Pontus), K. 87 (74a), is an early opera seria in three acts by Wolfgang Amadeus Mozart. The libretto is by Vittorio Amadeo Cigna-Santi after Giuseppe Parini's Italian translation of Jean Racine.

Mozart wrote Mitridate while touring Italy in 1770. It was first performed at the Regio Ducal Teatro, Milan, on the 26th of December 1770 (at the Milan Carnival). The opera was a success, having been performed twenty-one times despite doubts because of Mozart’s extreme youth — he was 14 at the time. No revival took place until the 20th century. This opera features splendid virtuoso arias for the principal roles, but only 2 ensemble numbers: the Act II ending duet between Aspasia and Sifare (Se viver non degg’io), and the brief quintet that ends the opera.

Information source: Wikipedia

The following performance is by Yvonne Kenny, soprano, and Anne Murray, mezzo, (originally composed for castrato).