Filling in, on one day's notice, will be 29-year-old American soprano Jennifer O'Loughlin. She was the cover singer for the role in this production at Salzburg last year, when Netrebko sang Susanna. Thus O'Loughlin and Netrebko are the only two sopranos who already know both the role and this staging — and Netrebko is not available.

A member since 2003 of the ensemble at the Vienna Volksoper, where she has sung Pamina, Musetta, Flotow's Martha and Britten's Tytania, among other roles, O'Loughlin has degrees from the Peabody Conservatory and the Manhattan School of Music; she took first prize in the 2003 Anneliese Rothenberger Competition in Germany.

O'Loughlin joins a cast including Dorothea R‹schmann, Gerald Finley, Martina Jankovš and Luca Pisaroni in Claus Guth's production; in the pit, Daniel Harding conducts the Vienna Philharmonic.

Damrau plans to return for the remainder of the run; O'Loughlin is so far confirmed only for tonight. In any event, there will be five more performances of this Figaro at the Salzburg Festival this summer, from tonight through August 28. Details are available at www.salzburgfestival.at.