prepositions - Is it "words in a song," "words to a song," or "words of a song"?

In

"I know the words in/of/to that song,"

do all three prepositions work equally fine?

Which is the most common?

Answer

I'm going to disagree with the other answer to this question. All three of these prepositions (in, of, to) can work. Without additional context, all refer to the entire lyrics of a song, and not just a portion. For example:

Outwardly, many of the Beatles' greatest hits are considered 'collaborations' between all four of the members of the band, but the words in those songs were written entirely by a single person, frequently John or Paul.

Here I chose "words in those songs" in order to contrast with "outwardly." This is just a style choice. It would not change the meaning in any way if I had instead chosen, "words to those songs," or, "words of those songs."

My personal feeling is that, in general, "words to a song" sounds the most idiomatic, but Ngram shows that "words of a song" is the most common:

(I agree that Ngram is a poor choice to highlight idiomatic differences between these prepositions, but it does help to check assumptions.)

Examples:

We can take the words of a song and set them to different music, or take the music and sing different words.

Jeff Morrow is correct that when we want to refer to a specific portion of a song, we do say "words in a song". For example:

In the process, the author observes the changes in America, from the earlier ones back during the Depression, where hard work was the key to achievement and “proud to be an American”” was more than words in a song.

Again, in this case the context indicates which words the writer means. Without this, you would assume the writer means all the words in the song.