An international body has said global revenue from music downloaded onto computers and mobile phones doubled to about $2 billion (€1.54 billion) in 2006.

But the digital business accounted for only about 10% of total music sales in 2006, and the surge in demand for downloaded  tunes had not offset a decline in sales of physical music such as compact discs, the International Federation of the Phonographic Industry said.

'By 2010 we expect at least one quarter of all music sales worldwide to be digital,' IFPI chairman and chief executive John  Kennedy said.

Currently, the split between global downloads made online and on mobile phones remains fairly equal, but varies substantially across markets, the IFPI said.

Revenue from single-track downloads is estimated to have totalled $795m in 2006, up 89% on 2005. Single-track downloads in the US totalled $582m last year, up 65%. European markets account for around 20% of global digital sales, but this is concentrated in the top markets - UK, France,  Germany, Italy and Spain.

IFPI represents the recording industry worldwide, with a  membership comprising about 1,400 record companies across 70  countries, according to its website.