The days of music distribution have changed. They're not changing, they've already changed. Nothing indicates this more easily than a leaked report from research brain trust NPD Group that indicates Apple, Inc. (NASDAQ: AAPL) has surpassed longtime #1 music retailer Wal-Mart Stores, Inc. (NYSE: WMT) as the world's largest music seller.

Here's the kicker -- Apple does not sell a single physical piece of music. It's all digital. The company's iTunes digital music store sells music, videos, television shows and movies to all those bazillions of iPod users around the world. Now, it just took out the world's largest retailer in terms of selling the most music. This even though Wal-Mart sells more CDs than anyone in addition to its very sizable music download service as well.

Apple passed Best Buy Inc. (NYSE: BBY) as the second-largest music retailer just recently, and now it's on top. All by using the mighty download as its vehicle of choice to get content to its customers. Is the music industry a different world than it was just five years ago? I'd say more like a different universe. Movies and television shows -- you could be next. In fact, the transition may already be far, far underway.