(It's pronounced "rivven" and once you say it a couple of times, the name is very hard to get out of your head.)
Read the synopsis of Ruddigore, but don't bother trying to find clips on YouTube. They're there but they're awful.
Every morning — or just about — I wake up with some snatchlet of music in my head. Some days it may take well past lunch for the theme from "What's Happenin'?'" to work its way out and I figure why should I suffer alone?