On the other side are a separate faction of label executives and a variety of artists, many of whom privately say they are worried that the chill cast on the mixtape world would handicap labels’ efforts to promote hip-hop sales, which declined roughly 20 percent last year, more than any other major genre, according to Nielsen SoundScan data.

Label executives remained puzzled over the sudden arrest of DJ Drama, whose ascent through the unregulated world of compilations has largely taken place in plain sight during the last couple of years. There has been speculation that the police inquiry into his business affairs was further spurred by tips from a competitor or unhappy customer. Chief Baker of the Morrow police declined to comment on the participation of any informants.

Mixtapes have been part of rap since the genre’s earliest days in the 1970s — back then, D.J.’s who spun records at clubs or parties committed their playlists to cassettes. But the proliferation of CD burners in the last several years has made the production and wide circulation — or sale — of mixtapes easier than ever.

It has also enhanced their role in tastemaking. Particularly since formerly underground mixtape hero 50 Cent broke out as a mainstream rap superstar in 2003, the top producers of unlicensed CDs have been embraced by the industry’s biggest corporations, who wager that the D.J.’s reputations as renegades will translate into the sale of legitimate, licensed compilations, too.

Atlantic Records, for one, hired the mixtape D.J. known as Sickamore as a talent scout and had signed DJ Drama, to its artist roster with plans to release an authorized mixtape-style album this year. Def Jam, Columbia and other big labels have released such CDs in the past.

Image DJ Drama, a prominent mixtape producer whose real name is Tyree Simmons, at party in Atlanta in November. Credit... Illustration by The New York Times

The labels’ reliance on the D.J.’s is complicated further by the fact that many of the top mixtape creators also double as radio D.J.’s on major rap stations. Many label executives acknowledge that when they write checks to certain D.J.’s to produce a mix CD for an artist, there is often an expectation that the D.J. will play the artist’s music on the air — an arrangement that recalls the industry’s recent radio corruption scandals involving illicit pay-for-play, or payola.