A cultural shift that eventually became a landslide began 10 years ago this month, though almost no one noticed at the time. Apple Inc. rolled out a portable MP3 player it dubbed the iPod, and after a promising opening quarter in 2002, sales dropped more than 50 percent.

The next year, Apple opened the iTunes digital music store; even though it held only 200,000 songs, a natural synergy was created with the iPod. Sales of the portable player quadrupled in 2004 to more than 4 million units. The pocket-sized player with the white ear buds was endorsed in iconic television commercials by bands and artists such as U2, Gorillaz, Feist, Daft Punk, Black Eyed Peas and Coldplay

Now the iTunes store is the single biggest music retailer in America, with more than 20 million tracks available and 160 billion songs downloaded since its launch. And the iPod is by far the most popular digital music player, commanding nearly 80 percent of the market and piling up a staggering 300 million sales since 2001.