Digital stores can offer a huge number of songs
Global digital music sales have almost doubled to around $2bn (£1bn) in 2006, according to an industry report.
But the rise, which represents 10% of all sales, has not reached the music companies' "holy grail" of offsetting the fall in CD sales.
The International Federation of the Phonographic Industry (IFPI) said digital sales could account for a quarter of all sales worldwide by 2010.
It also called for more action against illegal file sharing.
The IFPI's 2007 Digital Music Report said consumers last year downloaded 795 million tracks, up 89% on 2005, from almost 500 legitimate online music services available in 40 countries.
The number of tracks available for download doubled to reach over four million on leading services.
Despite this overall music sales were down 4% in the first half of 2006.
IFPI chairman John Kennedy said: "The pace of transformation in our industry is breathtaking, but at the moment the holy grail is evading us.
"I would like to be announcing that a fall in CD sales is being compensated for by an equal or greater increase in online and mobile revenues. But that is not yet happening on a global basis."
The IFPI said the 30,000 actions against illegal file-sharers globally had achieved some success against illegal file sharing but called for more action from internet service providers to stop such sites being set up.