Rock is no longer the country's most popular music genre -- at least not in volume.

That title would go to R&B and hip-hop, according to Nielsen. The research company found in its mid-year report that for the first time in Nielsen Music history, R&B/hip-hop has taken the largest share of volume, which measures album and track sales and audio and video streams.

R&B/hip-hop took 25.1 percent of volume, knocking out rock, which had always taken the largest share in the past. Rock slipped to second at 23 percent of the total volume, though it did still have over 40 percent of albums. R&B/hip-hop, however, dominated streams -- 30 percent of streams came from the genre, whereas rock only took 18 percent.

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Country still lags in streams, taking only a 5.6 percent share of volume. But physical albums and digital album purchases still remain strong at 14 percent and 12 percent of volume, respectively.

Out of the R&B and hip-hop genres, Kendrick Lamar and Drake stood out in particular.

Drake's "More Life" broke a record for audio on-demand streams in one week, with 385 million streams for its songs, trouncing the last record set by his previous album, "Views," which had 245 million streams in its first week.

Trailing close behind, Kendrick Lamar's album "DAMN" earned 341 million streams for its songs.