Every song ON DEMAND with ONE STUPID CATCH.
Here's the stupid catch: The first letter of each song and the last letter of the previous song must be the same. In other words, the first letter of the next song must be the same as the last letter of this song.
More stupid catches: The words "the" and "a" count. Words in parentheses do not count. Numbers are spelled out like words, and the letters "E" and "X" are open letter categories!