“The Music Genome Project’s database is built using a methodology that includes the use of precisely defined terminology, a consistent frame of reference, redundant analysis, and ongoing quality control to ensure that data integrity remains reliably high. Pandora does not use machine-listening or other forms of automated data extraction.”
via Music Genome Project.
Someday I hope to learn more about this project and the information it has produced. It would certainly provide an enormous wealth of data for training our algorithms!