Critical Metrics was a web-based music recommendation service. Unlike user-driven sites like The Hype Machine and Pandora, Critical Metrics featured only expert-generated content. Aggregating reviews and playlists from over 150 publications, both print and online, the site also encompassed historical sources. The site then ranked the songs mathematically, based on the information gathered. With a methodology based in the fields of bibliometrics and sentiment analysis, Critical Metrics quantified these positive citations and sentiments into indices for media playlisting and consumption.