I thought it would be a cool idea to make a thread listing some interesting facts about music: Eccentricities of composers, little known anecdotes about songs, and a general history of what makes human beings sing so much.
I'll start with 'musical puzzles'. These are cool little techniques some songwriters use to add variation and color to their music. They're fun to use because the technique involves a simple solution. All one needs to do is reverse any section of written music. In other words, learn to play both forwards and backward. It's also possible to play melodies and chords upside down as well.
Here's a cool fact. Ravel's 'Bolero' is an eight measure theme repeated over and over again with different variations for 17 minutes.