Neil Sedaka gave a surprise performance of his hits, including “Calendar Girl” and “Breaking Up Is Hard to Do,” at Clive Davis’ 80th-birthday bash Wednesday at the River Café. He also did a rendition of “Happy Birthday” for the music legend, based on his “Happy Birthday Sweet 16,” and motioned for songbird guests Aretha Franklin, Alicia Keys and Dionne Warwick to jump in. “Neil surprised Clive and . . . motioned to [the divas] to join him,” said a spy. “Everyone stood up, and they sang along.” Another guest at the party cracked, “Aretha looked like ‘You gotta pay me a lot of money to sing.’ ” The bash drew A-listers, including Jennifer Hudson, Joan Rivers, Elie Wiesel, Charles Koppelman and Allen Grubman. “Clive paid tribute to all his closest friends from his life,” said another guest. Davis added, of tragic Whitney Houston, with her brother Gary and sister-in-law Patricia, “We’re committed to dedicating ourselves to shepherding the incredible legacy of Whitney Houston and preserving her recordings.”