Rob Walker in the New York Times Magazine:
On first listen, some things grab you for their off-kilter novelty. Like the story of a company that has hired a bunch of “musicologists,” who sit at computers and listen to songs, one at a time, rating them element by element, separating out what sometimes comes to hundreds of data points for a three-minute tune. The company, an Internet radio service called Pandora, is convinced that by pouring this information through a computer into an algorithm, it can guide you, the listener, to music that you like. The premise is that your favorite songs can be stripped to parts and reverse-engineered.
Some elements that these musicologists (who, really, are musicians with day jobs) codify are technical, like beats per minute, or the presence of parallel octaves or block chords. Someone taking apart Gnarls Barkley’s “Crazy” documents the prevalence of harmony, chordal patterning, swung 16ths and the like. But their analysis goes beyond such objectively observable metrics. To what extent, on a scale of 1 to 5, does melody dominate the composition of “Hey Jude”? How “joyful” are the lyrics? How much does the music reflect a gospel influence? And how “busy” is Stan Getz’s solo in his recording of “These Foolish Things”? How emotional? How “motion-inducing”? On the continuum of accessible to avant-garde, where does this particular Getz recording fall?
There are more questions for every voice, every instrument, every intrinsic element of the music. And there are always answers, specific numerical ones. It can take 20 minutes to amass the data for a single tune. This has been done for more than 700,000 songs, by 80,000 artists. “The Music Genome Project,” as this undertaking is called, is the back end of Pandora.