Ledbelly:

It was midnight out on the sea
The band was playing "Nearer My God to Thee"
Cryin' "fare thee, Titannic, fare thee well"

While reading through this thread, I realized that I really like it when a song mentions another song, especially if it's a song I know. And if it's a song I don't know, the reference makes me want to hear it.

This Ledbelly song made me seek out the hymn, which I hadn't previously heard of, just as Eric Bogle's great ballad made me want to learn Waltzing Matilda (which until then I had assumed was a song about a kangaroo in a circus). And though I was disappointed in both cases and decided not to add them to my songbooks, I still have warm feelings toward both just because they're referred to in songs that I love.

I don't know why that is. In fact, it seems peculiar now that I think about it. But it might be something for songwriters to consider.