Directed by Lynne Taylor-Corbett, performances are scheduled for Aug. 26-30 at 8 PM.
Spirtas replaces previously announced Robert Cuccioli, who will begin performances Aug. 7 in Broadway's Spider-Man: Turn Off the Dark.
The cast also features Ashley Kate Adams, Tony winner Debbie Gravitte, Colin Hanlon, Fleur Phillips and Bryce Ryness. The artists will be accompanied by musical director Gerald Sternbach on piano.
Love Songs, according to press notes, "tells the tale of a wedding weekend at the Loews Regency Hotel. At the outset, the groom is stuck out of town on business and the bride has discovered that she's pregnant, while the other two couples, members of the wedding party, appear to be mismatched and ill-fated. As the piece runs its course, however, all is sorted out. Everything and everyone winds up in proper place for the nuptials. Happy ending!"
Feinstein's at Loews Regency is located at 540 Park Avenue at 61st Street. For ticket reservations call (212) 339-4095 or visit FeinsteinsAtLoewsRegency.com.