Schmaltz is way too much sappiness or sentimentality. A movie soundtrack that's dripping with emotion is full of schmaltz.
If a piece of music or a work of art goes overboard trying to make you feel sad or nostalgic, it's indulging in schmaltz. Love scenes in movies are too often guilty of schmaltz as well. Since the mid-1930s, the Yiddish word schmaltz has been used this way, although its original meaning is "rendered chicken fat," or "melted fat," first spelled shmalts. It comes from the Old High German smalz, "animal fat."