Make a connection between the song you post and the song posted before you. This could mean songs from different bands but with the same musician, songs that were covers of others, songs that came out in the same year, were next to each other on the billboard charts, sample from the same song, etc, etc. The more intricate the connection the better.
I'll start it off with an example:
[youtube]http://www.youtube.com/watch?v=tPBDMihPRJA[/youtube]
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((12+144+20+3*(4^(1/2)))/7)+5*11 = (9^2) + 0