Narn opera is a Narn art form. It is very expressive and robust with an emphasis on loud vocalizations. Although Narn opera is loved by most Narn, including G'Kar, most Centauri, including Londo Mollari, apparently find it repugnant.
When Mollari tried to trick Elric into being photographed with him for political gain, the Techno-mage cast several spells on the Ambassador as punishment for trying to use him in such a way. One of the tortures was a full measure of Narn opera.