I have always planned to go to a "Messiah from Scratch" where people just turn up, are provided with words and music and sing Handel's Messiah with no previous rehearsal, (ear plugs not always necessary).

My High School chorus had a tradition of doing the Halleluiah Chorus every year at the Christmas Concert. Any past members of the chorus present (and there always were many) were invited on stage and the audience was asked to sing along (music provided). Remains one of the most powerful musical experiences of my life, you should really do it, Jo.