Tempers were flaring at 5th and Arizona yesterday as an Unidentified Meanie tried to put the kibosh on an impromptu concert in front of the Santa Monica Post Office. The fun began shortly after 3:00 p.m., when an Impoverished Street Musician began playing a classic song from The Sound of Music, "My Favorite Things," on his guitar. There he was, strumming a happy tune, when suddenly -- somewhere between the "cream colored ponies" and "crisp apple strudel" -- the Meanie arrived on the scene, shouting, "Stop it, stop that racket right now!" "Why should I stop?!?," responded the Musician, " It's a free country!" "If you don't stop, I'll make you stop!," yelled the Meanie, who began screaming obscenities and waving his fist. The Musician, in response, played louder and louder, faster and faster, lending the piece enough frenzied passion to scare even Rogers & Hammerstein. Just when I thought they would start throwing "bright, copper kettles" at each other, the Meanie turned tail and rushed down 5th Street, threatening to return with the police. Some people just don't know when to shut their Von Trapps ...!