Pandora relies on complex computer software to grade it songs ... right? Not so, reports Rob Pegoraro at BoingBoing: About 25 music analysts at the company's Music Genome Project personally rank and quantify each song with up to 450 "genome units." For example, vocals are graded from 1 to 5 on "Melodic Articulation Clean-to-Dirty" (how well the melody hits the beat), "Delivery Spoken-to-Sung" or "Smooth or Silky" (Tom Waits' "Come On Up to the House" received an unsurprisingly low 1). Pandora's analysts, often hired by word-of-mouth in the Bay Area music scene, can analyze about 4 songs per hour, or 10,000 monthly.
Next, your playlists are are balanced by factors that balance relevance with variety—and that, writes Pegoraro, is where the company "lets me down most often." He finds the "talent pool can look a little shallow. Not just the same artists but the same albums crop up repeatedly." (Music researcher Jason Kirby raised a similar issue at Scholars' Lab a few years back, calling "homogeneity of songs' tempo an issue.") Other tidbits on the Genome Project: It doesn't care where you are (there's no "locavore listening"), and gives more weight to negative feedback than positive.