This week, the National Music Publishers Association sent a take-down notice to 50 sites, including Rap Genius, that "engage in blatant illegal behavior" by publishing song lyrics without a license. The NMPA is only targeting commercial sites that make money off those unlicensed lyrics and not personal blogs or fan sites.

The bulk of those 50 offenders are janky websites that take advantage of the five million Google searches of "lyrics" per day and make money off display ads. Popdust, which has raised $5.5 million from SoftBank Capital, Lerer Ventures, and New Enterprise Associates, is also on the list. But none are as well-funded and high profile as Rap Genius, which raised $15 million from Andreessen Horowitz to piggyback off its hip hop annotations to create an "Internet Talmud."

NMPA CEO David Israelite said the takedown notices "are a precursor to filing copyright infringement lawsuits," reports Billboard.com

His organization, on behalf of Warner Chappell Music, Peermusic and Bug Music, last year won a $6.6 million judgement against LiveUniverse, a company founded by Brad Greenspan that operated unlicensed lyrics sites. In 2010, the NMPA successfully sued Motive Force, a company that operated LyricWiki, and received an undisclosed amount of "funds associated with the exploitation of the unauthorized content."

In response to questions from Valleywag about whether Rap Genius anticipated a lawsuit and whether that factored into the size of its funding round, cofounder Ilan Zechory said:

We haven't heard anything from [NMPA] yet Nitasha - I'm sure we will soon :)

As with other publishers, we plan to meet them and teach them about Rap Genius (most people aren't aware that hundreds of classrooms are collaboratively annotating literature on RG right now, for example) and how it works, and also to learn about their relationship to writers and how all that works.

Rap Genius isn't a lyrics site; it's a monument to human knowledge. Once you understand what Rap Genius is you cannot possibly desire to shut it down. We see this is a great opportunity to get all musicians and authors involved in the project of adding insight and commentary to their works for everyone to enjoy.

We originally called the site "rap exegesis" - it was for fun, an art project. people enjoyed it and we enjoyed it, so we kept working on it. Very quickly people started using the site to close-read political speeches, bible verses, french poetry, and so on. That's the premise of the investment from Andreessen Horowitz - that the communities on Rap Genius will use the technology we build to create a lasting monument to human culture.

As Billboard notes, even if it the NMPA did move towards legal action, they should not expect the same kind of windfall: "It's unclear how much money is at stake. Rap Genius, for example, currently does not have advertising."

This isn't the first time Rap Genius has been questioned over its desire to monetize people Googling for song lyrics. Last year, the rap blog TUMBLIN' ERB accused Rap Genius of stealing its content from the music site Ohhla [the Original Hip-Hop Lyrics Archive]:

To contact the author of this post, please email nitasha@gawker.com.

[Image via Getty]