Apple’s iTunes store, which emerged in 2008 as the top U.S. music account for the first time, widened its lead last year over former market leader Walmart, according to a new report by “Billboard” (http://www.billboard.biz/bbbiz/content_display/magazine/upfront/e3i12fe2557a9382597671a522cc1cc901d).

Acording to the music industry publication’s analysis of 2009 sales and market share, the top 20 U.S. music accounts accounted for 85% of the total account base. That’s down from 88% in 2008 and runs counter to an almost decade-long consolidation trend under which the top 20 accounts continued to capture an ever larger share of the total market. “Brick-and-mortar” accounts dipped, while digital accounts made up a combined 35.5% of the total account base, up from 31.6% in 2008, says “Billboard.”

iTunes grew its share of the U.S. account base to 26.7%, up from 21.4% in 2008 and more than double the 12.7% share the company had in 2007. Number 2 account Walmart saw its 2009 share sink to 12.5% in 2009 from 15% in the prior year, and Best Buy, which is also reducing the store space it devotes to music, had only 8.7% of the account base in 2009, down from its pre-Napster share of 10.7% in 2008, according to “Billboard.”

According to Apple, the iTunes Store has a catalog of over 12 million songs, over 55,000 TV episodes and over 8,500 movies including over 2,500 in high definition video. As of February 2010, over 10 billion songs have been purchased and downloaded from iTunes.