Apple Inc.'s (NASDAQ: AAPL) popular iTunes store became the third largest music retailer in the United States, according to market research, soaring past traditional brick-and-mortar stores and other online stores.

iTunes accounted for 9.8 percent of all music sales in the first quarter, just behind Wal-Mart Stores, Inc., with 15.8 percent, and Best Buy, Inc., with 13.8 percent, according to market research firm NPD Group.

Both Wal-Mart and Best Buy sell traditional compact disks as well as online music, while iTunes only sells music over the Internet.

NPD said the iTunes digital music store had benefited from sales of Apple's iPod digital music player during the holiday season. Most songs sold from the store will only work on Apple's digital music player, although the company recently introduced a format that will work on any player.

The results put Apple ahead of larger, general purpose retailers in terms of music sales., Inc. dropped to fourth with a 6.7 percent share. Its sales increased but not as fast as its rivals.

Apple shares dropped 66 cents, or 0.54 percent, to $122.34 during normal trading hours on the Nasdaq Stock Market.