Rap Genius was founded as the "Wikipedia for rap," a people-powered community where rappers and fans post lyrics and annotate them with interpretations and historical facts. "Our aim is not to translate rap into "nerdspeak", but rather to critique rap as poetry," the site explains. Rap Genius grew rapidly, bolstered by search engine traffic for new albums. Only now, it's no longer just about rap.

Today the company announced a hefty $15 million investment from Andreesen Horowitz, a high-profile Silicon Valley venture capital firm which is invested in some of the highest-valued private social media companies including Twitter and Facebook. The money will be used to grow the site from an authoritative library of rap lyrics, with dozens of verified artist accounts including Murs and Nas, to a source of information on pretty much every kind of text.

"Poetry, literature, the Bible, political speeches, legal texts, science papers," Marc Andreesen wrote in a blog post today. "And those are just the start. We think the community will continue to expand beyond rap into all culture. The potential of this company is large." He compares the envisioned Rap Genius to the Talmud, the annotated version of the Torah.

"We think the community will continue to expand beyond rap into all culture."

Without annotations, Rap Genius would be up against the infinite legions of lyric sites. The annotations are also what sets it apart from sites like Quora and Wikipedia, which similarly depend on users to submit useful information in order to build a credible reference guide. By launching first in a niche topic, rap, the company built a core audience and tweaked the functionality until it had a workable mix of features. Now it can apply those lessons to building new communities around its next topics. No doubt Rap Genius's proven traction in rap made it an easy sell to investors (although translating its popularity into a business that can return on that big investment will be another feat altogether).

Rap Genius users have already started using the site to collaboratively annotate things like the Bill of Rights and Martin Luther King, Jr.'s "I have a dream" speech. These patches of non-rap texts fit a little awkwardly into the Rap Genius template, as the text will show up as "Bill of Rights Lyrics" unless the user remembers to tag the entry as "non-musical." For now, the new subjects will appear on Rap Genius next to the traditional fare, cofounder Ilan Zechory said, although the company may launch tangential sites in the future. The company will also defer to users when it comes to what new types of content to add. "This isn't really like a top-down approach," he told The Verge.

Rap lyrics are self-referential, obtuse, and layered with meaning, often requiring knowledge of context, history, and slang in order to be appreciated fully. Donovan Strain's viral blog post triangulating the exact date Ice Cube refers to in the song "Good Day" would have been a perfect fit for Rap Genius.

As with any user-driven site, Rap Genius's annotations range from superfluous to insightful. ("We're glad too Cube" reads the annotation on the line "I was glad everything had worked out.") The best annotations combine historical context with interpretation, the way a music critic might in a review. (The line "now I see her in commercials, she's universal" in Common's "I used to love H.E.R." has a subtext, as one user reveals: "While he used to complain about the ubiquity of rap in mainstream culture, Common himself has now sold out: Common has done ads for, among other businesses, Sprite, Gatorade and The Gap.") The more layered the song, the better the annotations: the explanation for 2pac's "Hail Mary" is a prime example, with contributions from Murs.

Founded in 2009, the site reportedly had 10 million unique visitors in May. The company has now hidden its traffic on Quantcast so it's no longer publicly-viewable, and Zechory was coy in an email: "But we don't even care about traffic, it's about being part of culture and having couples meet on the site."

Rap Genius has more than 50,000 followers on Twitter and more than 190,000 likes on Facebook. Andreesen says it is one of the fastest-growing sites in the history of the illustrious Y Combinator incubator, from which Rap Genius graduated in the summer of last year. The company is now headquartered in Brooklyn.

The site has a thriving community of users who compete to earn Rap IQ points for annotations that get good ratings from other users. Power users are promoted to editors who moderate the site, similar to Wikipedia. Right now, Rap Genius has more than 100,000 contributors and about 500 editors, Zechory said.

Gatsby_rap_genius

Rap Genius users annotate The Great Gatsby.

Rap Genius recently added video annotations and the Rap Map, a Google map annotated with historical events and significant places in rap like 2pac's elementary school. The company plans to add an iPhone app, Android app, private messaging, and fuller-featured profile pages.

When asked to describe his emotions post-announcement, Zechory directed The Verge to Gucci Mane's "Photoshoot," in which Mane raps, "2 girls on my bike, one on the back one on the handle bars." The annotation reads: "Gucci is so pimp that he has two girls on his bike — he doesn’t even need to have a car. WARNING: this is a dangerous level of pimp!"