A rare treat awaits opera aficionados today: A few days before their appearance in the much-anticipated «La Traviata,» two celebrated American opera singers join forces for one unique opera gala. Soprano Ruth-Ann Swenson and tenor Charles Castronovo are scheduled to sing at the Athens Concert Hall (Megaron) tonight. First visit «This is the first time I’m in Athens and I’m overjoyed,» said Swenson at a press conference last week. «I have already interpreted all the arias I will sing at the Megaron – either at gala performances or concerts – with the exception of Francesco Cilea’s piece.» The prominent, Long Island-born soprano is a well-known figure on world stages, having performed at landmark theaters including the Metropolitan Opera, the San Francisco Opera and Covent Garden, among others. Swenson rose to the top of her trade thanks to a winning combination: a warm, beautiful coloratura voice on the one hand, and sensational technique on the other. Castronovo also talked about his first appearance in Athens at the press conference. «It’s a new experience, in terms of the country, the place and the program,» he noted. «I have heard a lot on the subject of the Friends of the Concert Hall’s hall acoustics and I can’t wait to sing there.» Born in New York, Castronovo is considered one of the most interesting tenors of our time, having made his debut stage appearance as Alfred in Verdi’s «La Traviata.» The joint recital program features a number of landmark moments of Italian vocal music of the 19th century, complemented by French composer Charles Gounod (as French romantic opera has close ties to its Italian counterpart). The gala includes arias from beloved and well-known operas by Bellini, Donizetti, Rossini, Verdi, Gounod, Cilea and Weber. At the Athens Concert Hall tonight, the Athens State Orchestra will be conducted by Loukas Karytinos. Athens Concert Hall, 1 Kokkali & Vas. Sofias, tel 210.728.2333.