Swedish music streaming service Spotify is to halve the amount of time web users can listen to tracks for free.

From the beginning of May, users of the Spotify Open or Free service will get just 10 hours of listening time per month, instead of the current 20 hours. The streaming service says this is equivalent to around 200 tracks or 20 albums.

Spotify's free service lets users stream music over the web for no charge, although tracks are peppered with adverts just like commercial radio.

Furthermore, web users that signed up on or before November 1, 2010 will be able to play any one track a total of just five times. After this, they will need to purchase the track or sign up to one of Spotify's subscription-based services, which are priced from £4.99 per month.

New Spotify users will see these restrictions put in place after six months of service, but will initially enjoy 20 hours of free listening per month, while anyone who signed up after November 1 will see the cap put in place exactly six months after they joined.

"Spotify's aim from the very beginning was to make music on demand available to all. To give you the power to listen to, discover, share and manage your music the way you want to - simpler, faster, better - while making sure the artists whose music we all love continue to see the benefits as we grow," said Spotify CEO Daniel Ek in a blog.

"So it's vital that we continue offering an on-demand free service to you and millions more like you, but to make that possible we have to put some limits in place going forward."

The service currently has around 6.7 million users in Europe but only one million of those are paying subscribers. The service is currently in talks in regards to launching in the US.