natural sounds were used that would get louder or softer with distance. there are several songs including "to see you is to love you" by bing crosby, songs by nat king cole ("mona lisa", 1950) and dean martin ("that's amore", 1952), richard rodgers' song "lover" (1932), and "m'appari tutt'amor" from friedrich von flotow's opera "martha" (1844), and part of leonard bernstein's music for the ballet "fancy free" (1944).