82. The heroine of this work by Georg Frederich Handel (which is actually a secular oratorio, though it has been staged as an opera on occasion) pines after her absent love, and sings the lovely aria "Oh Sleep, Why Dost Thou Leave Me?".
From Quiz Sleepless at the Opera
Answer:
Semele
"Semele" recounts the tragic love of the mortal Semele for Jupiter, the god of thunder. In the second scene of Act II, Semele, awakening from her romantic reveries, calls upon sleep, to "...again deceive me; to my arms restore my wandering love". Semele's palace, in which she is kept by Jupiter, is guarded by two ever-wakeful dragons, which prevents the vengeful Juno from taking revenge on her rival. Juno calls upon Somnus, the god of sleep, and his attendant Morpheus to provide Jupiter with such an erotic dream of Semele that he will subsequently be unable to refuse any wish she may ask him to grant. She also obtains the rod of Somnus, which enables her to subdue the dragons guarding Semele's palace. She convinces Semele to ask Jupiter to come to her, not in his mortal form, but in his full glory as the god of Thunder. Jupiter is obliged to fulfill her request, which inevitably results in her fiery death. From her ashes, however, rises their son, the god Bacchus.
Semele's aria "Oh Sleep, Why Dost Thou Leave Me?" is one of the best-known arias from the oratorio, along with Jupiter's "Where E'er You Walk". The great tenor John McCormack was known for his performances of both of these arias, both of which he also recorded. His flawless trill in the opening phrase of "Oh Sleep" is counted as an example of his flawless technique, along with his celebrated octave leap in "Care Selve" (from Handel's "Atalanta- also an aria written for soprano) and his amazing single-breath phrase in "Il Mio Tesoro", from Mozart's "Don Giovanni".