There are lyric sites that just post the words to popular songs, and then there's Rap Genius. The five-year-old Brooklyn-based site that's a sort of Wikipedia for rap lyrics and their meanings has earned praise from users and a number of rappers for its insightful annotations to songs, which give visitors deeper understanding of what their favorite MCs are talking about.

What it doesn't do, according to a music industry trade organization, is pay for the right to post those lyrics.

The National Music Publishers Association sent takedown notices to Rap Genius and 49 other lyric sites on Monday arguing that they have engaged in "blatant illegal behavior" by posting lyrics written by their members alongside paid ad banners.

David Israelite, chief executive of NMPA, said that while Rap Genius may argue that what they do makes them unique from other lyrics sites, but "the idea that by commentary and analysis of copywritten material excuses them from any violation of copyright is preposterous."

"Imagine if you made movies available and at the end you offered some onscreen commentary," he said. "Could you then distribute those movies for profit without compensating the studios that made them? No." Israelite is demanding that the sites, which also include lyricsmania.com, lyricstime.com and songlyrics.com, either obtain the appropriate licenses right away or remove all copywritten material from their archives.

In an e-mailed statement to MTV News, Rap Genius co-founder Ilan Zechory said, "We can't wait to have a conversation with the NMPA about how all writers can participate in and benefit from the Rap Genius knowledge project. We don't believe this ends up in court, because it's a great website with overwhelming support from artists (look at all the verified artists using the site regularly), writers, and fans. We think sane, sensible people can see that and will look for ways to work together."

Zechory also said his site, unlike some of the others targeted, is more than a lyrics warehouse. "Rap Genius has crowdsourced annotations that give context to all the lyrics line by line, and tens of thousands of verified annotations directly from writers and performers," he said.

What Israelite noted, however, is that Zechory never claims that his site is covered under the "fair use" doctrine that grants exceptions to copyright law for the purpose of criticism, commentary or scholarship.

If they shut rap genius down, I'm gonna riot in this bitch

— Some call me Terez (@RealRichDreamz) November 13, 2013
"Their [Rap Genius'] statement doesn't use the term 'fair use' because they know it's not," Israelite said. "The most damaging evidence is that they've already licensed the biggest music publisher in the world, Sony, so they've basically admitted they need licenses."

Monday's action coincided with the release of a study of the worst lyric site offenders by University of Georgia professor and indie rock icon David Lowery (Camper Van Beethoven, Cracker). Israelite said the takedown notices came after two requirements were met: that the sites in question could have easily licensed the works in question and that they were making money off of unlicensed, copywritten materials. "We're not targeting fansites, blogs or education sites," he said. "Only the sites where the business model is trying to profit from using lyrics."

Israelite hopes that all 50 will get licenses and stay in business, or, if they refuse to share their profits with songwriters, cease and desist. The worst case scenario is that they continue doing what they're doing and force the NMPA to take them to court. "We've done it twice before against lyric sites and we won both cases," Israelite said.

"People are misinterpreting what's going on here. We're not trying to shut these sites down," he added.