iTunes sales may not be doing as well as the consistant sale of iPods may suggest, according to research analysts at Forrester Research.

After studying credit card transactions over the past 27 months, analysts say that since January the monthly revenue for iTunes has actually fallen by 65%. Apple doesn't officially release the figures for iTunes sales.

In an interview with The Register, one of the analysts cautioned against reading too much into the figures, but points out that there's no sign of the enormous growth in digital downloads that the music industry seem to expect.

Nielsen Soundscan has also analysed figures across the board for digital downloads, and says that revenues have been flat or declining for the last three-quarters.

The Forrester analyst points out that people are still buying CD, whether over the internet or in the shops, but aren't really that into downloaded songs that are copy-protected.

“iTunes sales are not cutting into CD sales”, Josh Bernoff told The Register. “They're an incremental purchase at best."

“There's a problem here. CD sales have fallen 20% over 5 years."

“The message here is not that CD sales are coming back, [but that] the ability to obtain pirated music is now so widespread the DRM looks to consumers more like a problem than a benefit.”