Stage and cabaret star Karen Mason won't be belting "Dancing Queen" and "Does Your Mother Know" much longer. The first of Mamma Mia's power trio (Mason, Louise Pitre and Judy Kaye) to exit, she'll leave the role of Tanya in early October. No word yet on who will replace her.

A star of the musical theatre and cabaret stage, Mason has appeared on Broadway in Sunset Boulevard, Jerome Robbins' Broadway and Torch Song Trilogy. Her Off-Broadway credits include And the World Goes 'Round and Carnival, and she has also been seen on the small screen in "Law & Order" and "As the World Turns." A four-time MAC Award-winning performer, Mason has charmed audiences at Carnegie Hall, Rainbow & Stars, Davenport's and L.A.'s The Cinegrill. Her solo recordings include "When the Sun Comes Out," "Not So Simply Broadway" and "Christmas! Christmas! Christmas!"

Mamma Mia! collects a couple dozen hit songs by the Swedish supergroup ABBA and shapes them around the story of a single mother and her young daughter, who gets married on a Greek isle. While the daughter plans her future with the love of her life, she and her mother are haunted by three different men who may or may not be her daughter's father.

Among the songs used in Mamma Mia! are such familiar seventies staples as "Dancing Queen," "Knowing Me, Knowing You," "S.O.S.," "Take a Chance on Me" and "The Winner Takes It All."

Mamma Mia! is directed by Phyllida Lloyd and choreographed by Anthony Van Laast. It is designed by Mark Thompson, with lighting design by Howard Harrison, sound design by Andrew Bruce and Bobby Aitken and musical supervision by Martin Koch. For tickets in New York, call (212) 239-6262. Mamma Mia! is on the web at http://www.mamma mia.com.