Presumably Italian opera tenor from the short story "Flavia and Her Artists" by Willa Cather, first published in the 1905 collection The Troll Garden. He is visiting at the home of arts patron Flavia Malcolm, who has stuffed her house with artist guests.
After Schemetzkin had grimaced and tortured the keyboard with malicious vulgarities for half an hour, Signor Donati, to put an end to his torture, consented to sing, and Flavia and Imogen went to fetch Arthur to play his accompaniments. Hamilton rose with an annoyed look, and placed his cigarette on the mantel. "Why yes, Flavia, I'll accompany him, provided he sings something with a melody, Italian arias or ballads, and provided the recital is not interminable."
His first name is not given.