Masters of the operetta Gilbert and Sullivan left the musical world a legacy of marvelously playful and tuneful songs. This entertaining medley includes We Sail the Ocean Blue and (I'm Called) Little Buttercup from“HMS Pinafore ” Overture and Three Little Maids from “Mikado ” and Poor Wand'ring One I Am the Very Model and With Cat-Like Tread from “Pirates of Penzance.”