David Petrou of the public relations agency of Eisner, Petrou & Associates, recently celebrated his 50thbirthday in style with a semi-centennial bash at the St. Regis Washington. The party was destined to be ahit from its inception—the clever, folded invitation featured one half of the face of Petrou as a youngboy, next to the other half of Petrou’s face as the 50-year-old birthday boy. Nearly 200 well-wisherswere in attendance to mark the big occasion. A number of them toasted the guest-of-honor, includingChoral Arts Society Music Director, Norman Scribner, who applauded the longtime chorus member. The partyspanned the hotel’s ballrooms and tented terrace, where revelers sipped blue martinis from the bar,enjoyed a cornucopia of sumptuous delicacies and danced to the soulful sounds of the legendary Drifters.