Today is St. Valentine’s day, one of the most popular of all saints’ days—not for any religious reasons, but because it has been associated for centuries with love and romance. It was a nice touch for Italian composer Riccardo Zandonai to get his new opera, “Giulietta e Romeo,” based on Shakespeare’s “Romeo and Juliet,” premiered in Rome on Valentine’s Day 1922. Today, Zandonai’s music is seldom heard outside of Italy, but the classic story of Romeo and Juliet has attracted a remarkable number of different musical settings. Many other operas on “Romeo and Juliet” have been written; the most famous being that by the French composer Charles Gounod, first staged in 1867. First runner-up, some distance away, is probably Bellini’s “I Capuleti e i Montecchi” of 1830. It’s intriguing to speculate what might have been if Tchaikovsky had ever followed through on his idea to write his own “Romeo and Juliet” opera. He made a few sketches, but instead of an opera he turned to the idea of a symphonic “fantasy-overture.” That became one of his most beloved concert pieces and is often quoted in movies and TV commercials as an instantly recognizable musical cue for love and romance.