) -- Compact discs may soon go the way of vinyl, as digital-music downloads are expected to equal CD sales by the end of next year.

According to market-research firm NPD Group, digital-music sales now make up 35% of the U.S. market, up from 30% in 2008.

The winner in this transition is easily


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, with its iTunes digital store selling more music than any other retailer in the country, including those that sell physical CDs. It's followed by

Wal-Mart Stores

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Best Buy

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Apple's Magical Mystery Event

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Apple owns 69% of the digital-music market, with


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following in a very distant second place, with 8% of the business.

NPD, however, does not track music-subscription services, such as RealNetworks' Rhapsody.

"The growth of legal digital-music downloads, and Apple's success in holding that market, has increased iTunes's overall strength in the retail music category," Russ Crupnick, entertainment industry analyst for NPD, said in a statement. "But the importance of the big-box retailers shouldn't be dismissed, as long as the majority of music consumers continue to buy CDs."

At least for now, people are still buying CDs, which account for 65% of music sales in the U.S.

Wal-Mart is the top CD seller, with a 20% share in the U.S. Best Buy has 16%, while Amazon and


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each account for 10%, NPD said.

-Reported by Jeanine Poggi in New York.

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