(Credit: DOB) Dutch mezzo-soprano Kaja Borris has died at the age of 77. Born on Jan. 8, 1939, Borris was born in The Hague and became an ensemble singer for the Deutsche Oper Berlin. The mezzo performed with the company for three decades, starting in 1971, performing such roles as Filipyevna in Tchaikovsky’s “Eugene Onegin,” Frau Marthe Schwerdtlein in Gounod’s {…}