The 82-year-old is Spain’s most famous opera singer and known around the world for her duet with former "Queen" singer, Freddy Mercury, on the song "Barcelona" which was the theme for the 1992 Olympic. BARCELONA, Spain (AP) — Montserrat Caballe. In a brief excursion into pop music, Caballe’s duet "Barcelona" with Freddie Mercury, of the rock group Queen, was a hit single in 1987, accompanied by a. BARCELONA, Spain (AP)…