Vivendi’s Universal Music has said it is to test the digital sale of songs from artists without the customary copy-protection technology.

It will allow the sale of thousands of albums and tracks available in MP3-form without the protection, known as digital rights management (DRM).

Most major recording studios insist music sellers use DRM technology to curb on-line piracy.

Universal artists include 50 Cent, the Black Eyed Peas, and Amy Winehouse.

Universal said: “The experiment will run from August to January and analyse such factors as consumer demand, price sensitivity and piracy in regards to the availability of open MP3s.”

Retailers including Google, Wal-Mart and Amazon.com, will participate in the DRM-free trial, Universal said.

But participants do not include Apple iTunes on-line music store, the third largest music retailer in the US or Microsoft MSN.