“L’Elisir d’Amore” — “The Elixir of Love” — is what’s known as an opera buffa, or comic opera. That means that we’re in for a happy ending.But Donizetti knows that the payoff is only earned through the suffering of his protagonists. In one pivotal moment, our hero Nemorino glimpses his beloved shedding a single tear — and he concludes (crazily, but correctly) that it can only mean that she loves him back. The aria Nemorino delivers here — one of the most famous in the history of opera — expresses the singular moment when the agony of unrequited love shifts to the certainty of a blissful future.In this episode, host Rhiannon Giddens and her guests unpack the potential for heartbreak that lies within every happy ending and why Donizetti might be one of the most underrated opera composers. Tenor Matthew Polenzani brings it home with a rendition of “Una furtiva lagrima” from the Met stage.THE GUESTSOver the course of a career spanning more than 30 years, tenor Matthew Polenzani has sung the role of Nemorino on opera stages all over the world. He has a family of barbershop quartet singers to thank for his introduction to music.Fred Plotkin is the author of “Opera 101: A Complete Guide to Learning and Loving Opera.” As a proud Donizetti fanboy, he believes that the psychological insight Donizetti brings to his characters is nearly unmatched in the work of other composers.When she’s not teaching French at St. Mary’s College of Maryland, Laine Doggett is brushing up on her medieval lore. As the author of “Love Cures: Healing and Magic in Old French Romance,” she knows a thing or two about magical elixirs.Judith Fetterley is a former professor, master gardener, and writer. She’s got a love story of her own that involves elixirs. You might have read it in the New York Times’ “Modern Love” column under the title, Was She Just Another Nicely Packaged Pain Delivery System?