Only Wal-Mart sells more music than iTunes
Apple continues to tighten its grip on music sales as iTunes has become the second largest U.S. music retailer.
A report released by tracking company NPD Group, showed that Apple now has more than 50 million customers and sold more than 4 billion songs last year.
Apple's digital music store jumped past Best Buy to capture the No.2 spot behind Wal-Mart stores. Apple is on a roll. It was only last June that the company overtook Amazon as the nation's third-largest retailer.
How long before the company can surpass Wal-Mart to become top dog in music sales?