Work on music (not necessary sounds) is carried out by the Music Genome Project (http://en.wikipedia.org/wiki/Music_Genome_Project http://en.wikipedia.org/wiki/

Work on music (not necessary sounds) is carried out by the Music Genome Project (http://en.wikipedia.org/wiki/Music_Genome_Project http://en.wikipedia.org/wiki/Music_Genome_Project). It's the engine behind Pandora. There's an incomplete list of attributes used in this classification here: http://en.wikipedia.org/wiki/List_of_Music_Genome_Project_attributes http://en.wikipedia.org/wiki/List_of_Music_Genome_Project_at.... They still use manpower to classify all those tracks which makes it very hard to scale.