Vivendi's Universal Music has said it is to test the digital sale of songs from top selling artists, such as Amy Winehouse, without the customary copy-protection technology, known as digital rights management (DRM).

Advert: Pinsent Masons is recruiting. Find out more.The decision will allow the sale by certain online retailers of thousands of albums and tracks available in MP3-form without the protection.

Most major music publishers insist music sellers use DRM technology to curb online piracy, effectively stopping the recordings being unlawfully copied and shared by consumers.

Apart from Amy Winehouse, Universal's most popular artists include 50 Cent and the Black Eyed Peas.

"The experiment will run from August to January and analyze such factors as consumer demand, price sensitivity and piracy in regards to the availability of open MP3s," a spokesman for Universal told BBC News.

According to Universal, retailers including Google, Wal-Mart, and Amazon.com, will participate in the DRM-free trial.

But participants do not include Apple iTunes online music store, the third largest music retailer in the US.

DRM technology is controversial because it restricts a consumer's use of bought music to a greater degree than records or CDs do.

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