It was bound to happen. After it has announced yesterday that it will start selling DRM Free tunes through a new virtual store, MusicPass, Sony BMG announced today a partnership with Amazon MP3 store.

The initiative "is the newest element of our ongoing campaign to bring our music to fans wherever they happen to be," Thomas Hesse, who's president of Sony BMG's global digital business and U.S. sales, said in a statement.

The irony is that Sony BMG is the last company to drop DRM protection, after Bertelsmann was the first company that introduced the technology back in 2002.

By nailing down distribution deals with all four major music companies, Amazon MP3 store is on his way to become the most powerful competitor of the almighty iTunes.

Amazon MP3, which was launched last year in September, is selling the songs at 89 cents, making the offer even more interesting for potential buyers, because iTunes sells tracks for 10 cents more.

In fact, Amazon's clear aim is to attract unsatisfied customers from Apple's iTunes, currently the third largest music retailer in the US and the most powerful music download service on the Web. Despite Apple's clear dominance in the digital music industry, the presence of DRM software in almost every song sold through the online store is keeping a lot of potential customers away and it definitely frustrates others, who have to buy an iPod and only an iPod to be able to listen their favorite songs.

And now, with all the major labels on Amazon’s bandwagon, maybe Apple should start paying attention to its competitor. While Amazon is selling DRM free songs from Universal Music, Warner Group, EMI and now Sony BMG, EMI is the only company that has a similar deal with Apple.

What is also ironic is that none other than Apple’s CEO, Steve Jobs, has started the DRM free revolution after he published in 2007 his famous letter, Thoughts On Music. You know, Steve, be careful what you wish!

On the other hand, now we have another reason to stay focused on Apple’s next event MacWorld Expo, which is scheduled to start on January 15.