Rao’s owner Frank Pellegrino entertained guests at another Italian restaurant this week when he showed up to dine at Fresco by Scotto and sang Frankie Valli’s “Oh, What a Night.”

Guests enjoying the tune included NYPD Commissioner Bill Bratton, wife Rikki Klieman and former mayoral candidate Bill Thompson.

Spotted at the bar was Diahann Carroll, days after the former “Dynasty” diva pulled out of “Raisin in the Sun” on Broadway with Denzel Washington.

A spy said Carroll was having what looked like a quiet “business meeting” with two people. Lining up another gig? She exited “Raisin,” which starts previews March 8, claiming it was because of the intense performance schedule.