Sound recognition services are provided by a number of companies, many of which license these services for a fee. Nothing is cheap, requiring significant signature / music catalog repositories and processing power. Check out the people who own the technology used by Shazam - Landmark Digital Services , the makers of Soundhound - Midomi , or Gracenote MusicID . There are others, but these are probably three of the biggest players at the moment.
UPDATE (11/8/12): It should be noted that Shazam seems to have acquired the rights to recognition technology, and Landmark Digital is no longer functioning. In addition, as noted in another answer, EchoNest now provides recognition technology. (However, EchoNest is no longer free.)
rcw3 Apr 26 '11 at 4:40 2011-04-26 04:40
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