Playwrights Horizons (Tim Sanford, Artistic Dir; Leslie Marcus, Managing Dir) will hold its annual Spring Gala on Mon May 9  at the event space 583 Park Avenue.  The evening will celebrate those writers and artists who trace the beginnings of their careers to Playwrights Horizons, and the funds raised will support the programs that continue this legacy.   The event will feature music by alumni writers Adam Guettel, Robert Lopez, Jeanine Tesori and Chris Miller & Nathan Tysen.  A full slate of performers will be announced in the coming weeks. The evening will honor Playwrights Horizons board member Stefanie Kane. Ms. Kane leads the U.S. Entertainment, Media & Communications Assurance practice for PricewaterhouseCoopers LLP (PwC). Serving as Gala Co-Chairs are Betsy Fippinger, Sam Gonzalez, Bruce Horten and Aaron Lieber. Cocktails and a Silent Auction will begin at 6:00 PM, followed at 7:30 PM by dinner and the evening’s entertainment. For tickets, please visit at www.PHnyc.org. Press contact: Michael Borowski/The Publicity Office (212/365-6849)...