Complex sentence: Cissy, Wilf, and Reg are all retired members of an operatic quartet, living in Beecham House, a retirement home for gifted musicians, who put on a concert on Giuseppe Verdi's birthday every year.
Split into simpler sentences: Cissy, Wilf, and Reg are all retired members of an operatic quartet, living in Beecham House, a retirement home for gifted musicians. The residents of the house put on a concert on Giuseppe Verdi's birthday every year.