I had the most interesting experience yesterday.  I was on Amazon and checking out a record of art songs.  At first I couldn't hear it, then I realized my sound was off.  I turned it on and heard wonderful Celtic music, which surprised me, sung by a lady.  Then a classical baritone came in quietly in the background, but after a few seconds grew loud as the Celtic grew quiet.  Then the Celtic grew loud again and they both sang loud, but in perfect counterpoint.  It may well be the most beautiful sound I ever heard.  I got excited, and determined to buy the album.  Then I realized I had Celtic music playing on Windows Media Player - two songs played at once, the beauty a coincidence.