The best way to spread Christmas cheer
is singing loud for all to hear!
-Buddy in Elf

In the Christmas movie Elf (2003), Jovie (played by Zooey Deschanel) must "spread Christmas cheer" to help Santa. She chooses to sing "Santa Claus is coming to town," and soon all of New York City is singing along.

The best sing-along songs are short and have lyrics that repeat. Jovie's choice, "Santa Claus is coming to town," satisfies both criteria. The musical structure of the song is simple:

• Verse 1: You better watch out / You better not cry / Better not pout / I'm telling you why
• Tag line: Santa Claus is coming to town
• Verse 2: He's making a list / And checking it twice; / Gonna find out / Who's naughty and nice
• Tag line repeats
• Bridge: He sees you when you're sleeping / He knows when you're awake / He knows if you've been bad or good / So be good for goodness sake! / O!
• Verse 1 repeats
• Partial tags and final tag: Santa Claus is coming / Santa Claus is coming / Santa Claus is coming to town

There is a fun way to visualize repetition in song lyrics. For a song that has N words, you can define the repetition matrix to be the N x N matrix where the (i,j)th cell has the value 1 if the i_th word is the same as the j_th word. Otherwise, the (i,j)th cell equals 0. You can visualize the matrix by using a two-color heat map. Colin Morris has a web site devoted to these visualizations.

The following image visualizes the lyrics of "Santa Claus is coming to town." I have added some vertical and horizontal lines to divide the lyrics into seven sections: the verses (V1 and V2), the tag line (S), and the bridge (B).

The image shows the structure of the repetition in the song lyrics:

• The first verse contains the repetition of the words 'you', 'better', and 'not'.
• The second verse repeats only the word 'out' from Verse 1.
• The bridge repeats the word 'you', which appeared three times in Verse 1. It also repeats several words ('when', 'knows', 'good', ...) within the bridge.
• The tag line "Santa Claus is coming [to town]" is repeated a total of five times.

Now that you understand what a repetition matrix looks like and how to interpret it, let's visualize a few other classic Christmas songs that contain repetitive lyrics! To help "spread Christmas cheer," I'll use shades of red and green to visualize the lyrics, rather than the boring white and black colors.

### The Twelve Days of Christmas

If you make a list of Christmas songs that have repetition, chances are "The Twelve Days of Christmas" will be at the top of the list. The song is formulaic: each new verse adds a few new words before repeating the words from the previous verse. As a result, the repetition matrix is almost boring in its regularity. Here is the visualization of the classic song (click to enlarge):

### Little Drummer Boy

Another highly repetitive Christmas song is "The Little Drummer Boy," which features an onomatopoeic phrase (Pa rum pum pum pum) that alternates with the other lyrics. A visualization of the classic song is shown below:

### Silver Bells

In addition to repeating the title, "Silver Bells" repeats several phrases. Most notably, the phrase "Soon it will be Christmas Day" is repeated multiple times at the end of the song. Because only certain phrases are repeated, the visualization has a pleasing structure that complements the song's lyrical qualities:

### Silent Night

To contrast the hustle, bustle, and commercialism of Christmas, I enjoy hearing songs that are musically simple. One of my favorites is "Silent Night." Each verse is distinct, yet each begins with "Silent night, holy night!" and ends by repeating a phrase. The resulting visualization is devoid of clutter. It is visually empty and matches the lyrical imagery, "all is calm, all is bright."