Clive Davis didn’t let the rain dampen his Memorial Day party on Saturday at his Pound Ridge estate. Joan Rivers, Patti LuPone, Neil Sedaka, Valerie Simpson, the New York Post’s Michael Riedel, Arnold Stiefel and Nikki Haskell were among more than 60 guests who were heralded into the main house, where music of Daft Punk, Justin Timberlake and Pink played. Later, we’re told the group was greeted by a legion of 30 umbrella-wielding attendants who escorted them to the record mogul and current chief creative officer of Sony Music Entertainment’s guest house for a lavish sit-down dinner to a soundtrack of Frank Sinatra, Aretha Franklin and Rod Stewart. To cap off the night, guests took the stage in Davis’ home theater to take part in a comedy competition. No word on who won, but we’re told Rivers sat it out, sitting in the audience regaling everyone with witty asides.