Entertainment event apparently organized by Maxwell Smart.

When he hears the Chief perform an impromptu rendition of "Heart of My Heart" Max is so impressed that he immediately puts him down for the lead. [Episode #14: "Weekend Vampire".]

Oddly, two years later, this seems to have slipped Max's memory given his extremely dubious reaction to the Chief's plan to go undercover as a singing waiter at the KAOS-operated restaurant The Mustache Cup. [Episode #84: "The Hot Line".]