Cupertino (CA) - Apple announced that it’s iTunes music store now has 50 million customers and has become the second largest music retailer in the U.S.

According to the company, more than four billion songs have been sold through iTunes so far; the store catalog now holds six million different titles. According to NPD Group, the only U.S. store selling more music than Apple is Wal-Mart.

iTunes recently has been under fire by customers who complain about Apple’s policy to charge for the removal of DRM-protection from music tracks. While the company sells both DRM-protected and not-protected songs for $0.99 users have to pay $0.30 per song or 30% of the album price to remove DRM protection.

Also, DRM can only be removed from an entire music collection and not just individual songs. For example, a collection of 1000 songs that was purchased for $990 will cost the consumer an additional $300 to get rid of the integrated DRM.