[Originally posted Oct. 28 at Fortune.com.]
Steve Jobs likes to describe Apple's (AAPL) business model as a stool built on three-legs: the Mac, the iPod and the iPhone.
But a quick glance at the 2009 Form 10-K, which Apple filed on Tuesday, shows that it is now more like a four-leg chair, with a couple of wedge-shaped pillows on the side.
The Mac and iPod still bring in the biggest part of Apple's total sales revenue -- 37.7% and 22.1%, respectively -- but their shares of the pie are shrinking.
The iPhone, meanwhile, is rapidly catching up, thanks to unit sales that grew 78% and GAAP revenue (swelled by deferred revenue dating back to 2007) that grew 266%. The iPhone now accounts for 18.5% of Apple's sales, just behind the iPod.
The fourth leg of the chair is the line item Apple calls "other music related products and services" but which is mostly iTunes Store sales -- music, video and apps. It continues to grow at a steady pace and now represents about 11% of Apple's net sales.
Spreadsheets summarizing Apple's revenue streams are pasted below the fold. Apple's 2009 Form 10-K is available as a pdf file here.
[Follow Philip Elmer-DeWitt on Twitter @philiped]
Net sales by product in millions.
Share of total revenue by product.