Singer James Taylor, 52, and his girlfriend of eight years, Caroline “Kim” Smedvig, 46, married in a Boston church on Sunday before about 50 friends and family members. John Williams, the Hollywood film composer (“Star Wars”) and Boston Pops conductor laureate, gave Smedvig, an executive with the Boston Symphony Orchestra, away. Sir Andre Previn and Yo-Yo Ma performed at the wedding, according to a rep for the couple. Taylor’s previous marriages were to singer Carly Simon (1972-82) and to actress Kathryn Walker (1982-96). This is Smedvig’s second marriage.