Spotify launched in 2008 and now has 40 million active users in 56 countries, three quarters of whom use the free service rather than the paid-for subscription.
That compares to the 24 million active users, including around six million premium customers, the company reported in April 2013.
Spotify's catalogue is one of the widest available on streaming services, but Eminem did not have to face the stiff competition of The Beatles, who were still not available in the Swedish company's offer.
The most popular female artist was Rihanna.
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Spotify discreetly publishes its financial results from Luxemburg, where it is headquartered.
In its latest report for fiscal year 2012, published last year, the company reported net losses of 58.7 million euros (USD 80.2 million) and a 434.7-million-euro revenue.
In its statement today, the group also revealed that "more than one billion dollars" had been payed to the copyright holders since 2000, roughly double the amount paid a year earlier.