from Wikipedia
Christmas music is a genre which is normally performed during the time period leading up to, and sometimes shortly past, Christmas. Christmas songs frequently are the focus of holiday themes directly taken from Christmas, but occasionally they have no content addressing the holiday, and instead focus on the winter season as a whole. These songs recognisably fall into several different groupings, depending on both the time and melody of the songs.

Songs which are traditional, even some without a specific religious context, are often called Christmas carols. Some songs of more recent vintage, often introduced in films, are specifically about Christmas, but are typically not overtly religious and therefore do not qualify as Christmas carols. The archetypal example is 1942’s “White Christmas”, although many other holiday songs have become perennial favourites, such as Gene Autry’s “Rudolph the Red-Nosed Reindeer”.

A significant subset of the secular songs are regarded as “Christmas” songs due to the time of year that they are most often sung, despite never mentioning anything about Christmas. These songs include traditional favourites such as “Winter Wonderland” and “Sleigh Ride” (whose standard lyrics mention not a holiday party but a birthday party). These songs fall into the generic “winter holiday” classification, as they carry no religious connotation at all. However, it could be argued that it would be impossible to popularise a winter-themed song, especially in the United States, without its being regarded as a “Christmas” song. In fact, winter-themed songs are generally not played on the radio in the U.S. during the larger part of the winter after the Christmas season has ended.

Another subset of the popular holiday songs, apart from the more sincere ones, are the many parodies or twists on existing songs, which are usually classified as "Novelty songs". They range from the cuteness of "The Chipmunk Song", by Alvin and the Chipmunks, to the Cold War gallows humor of "Christmas at Ground Zero" and the morbid humor of "The Night Santa Went Crazy", both by "Weird Al" Yankovic.

Some songs have little relationship to Christmas, but are hyped up over the period. Each year, record companies compete for the Christmas number one single spot, usually, but not always, with a Christmas-related song. This is parodied in the film Love Actually, whereby an artist records a cover version of a song and adds a Christmas twist to it, all the time admitting that it is "rubbish".

In the United Kingdom, Cliff Richard is famed for his many attempts, with some success, to get the Christmas number one single.