Despite the success of Apple iTunes, few people stock their iPod with tracks from the online store, reports a study.
Most of the music on an iPod is not from iTunes, reveals report
The Jupiter Research report says that, on average, only 20 of the tracks on an iPod will be from the iTunes shop.
Far more important to iPod owners, said the study, was free music ripped from CDs someone already owned or acquired from file-sharing sites.
The report's authors claimed their findings had profound implications for the future of the online music market.
They estimate that during 2006 Europeans will spend more than 385m euros (£260m) on digital music - the majority of this spending will be on tracks from Apple's iTunes store.
However, the report into the habits of iPod users reveals that 83% of iPod owners do not buy digital music regularly. The minority, 17%, buy and download music, usually single tracks, at least once per month.
On average, the study reports, only 5% of the music on an iPod will be bought from online music stores. The rest will be from CDs the owner of an MP3 player already has or tracks they have downloaded from file-sharing sites.
The report warned against simple characterisations of the music-buying public that divide people into those that pay and those that pirate.
"It is not instructive to think of portable media player owners, nor iPod owners specifically, as homogenous groups," warned the report.
It said: "Digital music buyers do not necessarily stop file-sharing upon buying legally."
The importance of "free" to digital music fans should not be underestimated, warned the report, and should be a factor for newer digital music firms, such as Spiral Frog, which use an ad-supported model.
Perhaps the only salient characteristic shared by all owners of portable music players was that they were more likely to buy more music - especially CDs.
"Digital music purchasing has not yet fundamentally changed the way in which digital music customers buy music," read the report.