Music act Three 6 Mafia couldn't have won an Oscar for the song "It's Hard Out Here For A Pimp" without support from the folks behind the film Hustle And Flow. Similarly, portable music players--or PMPs--are expected to double within six years thanks to the support of the explosive online digital content market.

According to iSuppli, PMP shipments will rise to 268.6 million units in 2011 from 128.7 million units in 2005. And revenues will increase to $21.5 billion from $14 billion in 2005.

PMP growth is parallel to growth in the digital content market, iSuppli says--for example, the online paid video space will grow to $4.5 billion in 2010 from $300 million in 2006. I also credit the increase of niche sites (check out "Sites For Sore Ears" in the Feburary 12, 2007 print edition of Red Herring) that help music lovers find what they're looking for without having to navigate the gargantuan collection of iTunes.

However, it's doubtful that all PMPs will benefit equally. Microsoft's Zune, billed as the most likely of iPod killers, underwhelmed the market despite media hype (see "Are Dell and Microsoft Out Of Ideas?"). And Piper Jaffray analyst Gene Munster, who covers Apple for the firm, once told me that on a plane he sat next to a guy who had one of Creative's Zen players--and he was thumbing through the iPod accesories section of the on-flight magazine (read "The iPod Wannabes" in the September 4, 2006 issue).

Hey, at least the bigger pie means a bigger piece for all player-playas.