One of the things the press and analysts think will come out of Amazon's (NASDAQ:AMZN) earnings is a look at whether its digital music store is gaining any ground on Apple's (NASDAQ:AAPL) iTunes. Not likely.

According to The Wall Street Journal, "With information on the efforts' results hard to come by, analysts are likely to look closely for data on how they're faring when Amazon reports quarterly earnings." While some research shows that the Amazon product has made a bit of headway, over 80% of music downloads in the US come from iTunes.

Amazon's problem is remarkably simple and nearly impossible to solve. No only was Apple in the music download business five years ago, it also has a device to go with the service. By most estimates Apple has sold more than 120 million iPods and that figure goes up by the millions as each new quarter passes.

Apple, essentially, has a matched pair, a device and a software service to supply the content which the iPod uses. Until Amazon has tens of millions of its own MP3 players in the market, it needs to stick to selling books.

Douglas A. McIntyre is an editor at 247wallst.com.