Yvonne Naef will replace Lieberson in the role of Mulier Samaritana, according to a Boston Symphony spokesperson. Naef was to sing the second mezzo-soprano part of Maria Aegyptiaca; Jane Henschel has agreed to fill in for Naef.
The spokesperson could not give a reason for Lieberson's withdrawal, but a brief article in the New York Times said the cause was illness.
The performance, to be conducted by BSO music director James Levine, will also feature sopranos Deborah Voigt and Heidi Grant Murphy, tenor Johan Botha, and bass John Relyea.