UK music fans have legally downloaded more than 500,000 songs so far this year, industry figures show.
Coldplay are one of the UK's biggest-selling bands
The biggest-selling download of the year to date is Coldplay's 2,000 Miles, just ahead of OutKast's Hey Ya!.
The half-a-million barrier was broken just a week after the UK launch of Napster, whose sales are not included in the figures.
The British Phonographic Industry's (BPI) figures also reveal that the cassette single has died as a format.
In the first quarter of 2003, £418,000 worth of cassette singles were sold - but there were no shipments in the first three months of this year.
The lack of shipments "effectively marked the demise of the format", said the BPI.
But the UK music industry will be buoyed by the growth in legal downloads. That market was practically non-existent this time last year.
BPI chairman Peter Jamieson said: "With 500,000 legal
downloads sold already this year, we have hit yet another milestone in the development of this exciting new market for music.
"This is shaping up to be a breakthrough year for the music industry."
UK MUSIC INDUSTRY
Album sales down 3%
Music DVD sales up 22.5%
CD singles down 32.1%
7-inch vinyl up 47.8%
Source: BPI. All figures are Jan-Mar 2004 compared with Jan-Mar 2003.
The first quarter of 2004 also saw a 47.8% rise in the sales of vinyl 7-inch singles.
But CD single sales dropped by almost a third on the same period last year, while CD album sales were down almost 3%.
The BPI said the small decline in CD album sales would "come as a relief in an industry which has seen double digit declines in some major markets".
Album sales account for more than 90% of the UK industry's revenue.
The total value of the UK music industry fell 4.3% in the first three months of 2004 compared with the same period last year.
But figures for the full 12 months to March show CD album sales rose 3.8% compared with the previous year, while the overall value of the market grew 3%.
"The fact that album sales continue to show such resilience is a good start to what many had predicted would be a tough year for music," said the BPI in its quarterly review.