Some songs are hits – Number One for a couple of weeks. Some songs are standards – they endure decade after decade. And a few very rare songs reach way beyond either category, to embed themselves so deeply in the collective consciousness they become part of the soundtrack of society. They start off the same as all the other numbers, written for a show or a movie, a singer or an event, but they float free of the writer, they outlast the singer, transcend the movie, change the event. In White Christmas: The Story of an American Song, Jody Rosen makes the case that the subject of his book transformed the American Christmas. There are a couple of what we now think of as seasonal standards that predate Irving Berlin’s entry into the field, but neither became a pillar of the Xmas repertoire, because until ‘White Christmas’ came along there was no such thing. (‘Jingle Bells’ was written for Thanks- giving.) In the decade after Bing Crosby introduced the number in Holiday Inn (1942), Berlin’s colleagues responded with ‘Let It Snow, Let It Snow, Let It Snow’, ‘Rudolph the Red-Nosed Reindeer’, ‘Have Yourself a Merry Little Christmas’, ‘Frosty the Snowman’ – all the ‘Yule Day gravy’ (as Variety put it) that in a slightly different order makes up every Christmas album from Andy Williams to ‘N Sync. Rosen doesn’t say so, but, in a fragmented culture, these are now the last songs we all sing, whether our tastes incline to rap or country or the Mormon Tabernacle Choir. They represent the zenith of a universal popular culture we’re unlikely to see again.