Activision Blizzard Inc. said Friday that a unit has bought FreeStyleGames, a United Kingdom developer of music-based video games.

The Santa Monica video game publisher of the popular “Guitar Hero” video game franchise said the acquisition by Activision Publishing Inc. is an effort to expand its global leadership position in the music-based genre. Financial terms were not disclosed.

“Guitar Hero” games have sold more than 22 million units worldwide since the franchise’s inception. FreeStyleGames is developing localized downloadable content for the Guitar Hero franchise, Activision said, as well as new games in the music genre.

Activision Blizzard was formed earlier this year when France’s Vivendi SA bought a majority stake in Activision Inc. FreeStyleGames becomes a wholly owned subsidiary of Activision Publishing and will continue to be based in Leamington Spa, U.K.

Activision Blizzard shares were down 18 cents, or 1 percent, to $17.60 in morning trading on the Nasdaq.